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Research in genetics in this department employs a variety of organisms, ranging in complexity from bacteriophage to humans. Several groups are studying the process of transmission of genes by analyzing DNA replication, DNA repair, chromosome segregation and cell division.
The use of genetics to identify regulatory genes and to define biological mechanisms is a crucial tool in unraveling a myriad of biological problems. Among the processes being investigated via genetics by members of this department are aging, human genetic diseases, human spermatogenesis, cell death, neurobiology, developmental biology, protein processing and secretion, the cytoskeleton and cell architecture, and plant-bacterial communication.
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The information in genomes provides the instruction set for producing each living organism on the planet. While we have a growing understanding of the basic biochemical functions of many of the individual genes in genomes, understanding the complex processes by which this encoded information is read out to orchestrate production of incredibly diverse cell types and organ functions, and how different species use strikingly similar gene sets to nonetheless produce fantastically diverse organismal morphologies with distinct survival and reproductive strategies, comprise many of the deepest questions in all of science. Moreover, we recognize that inherited or acquired variation in DNA sequence and changes in epigenetic states contribute to the causation of virtually every disease that afflicts our species. Spectacular advances in genetic and genomic analysis now provide the tools to answer these fundamental questions.
Members of the Department of Genetics conduct basic research using genetics and genomics of model organisms (yeast, fruit fly, worm, zebrafish, mouse) and humans to understand fundamental mechanisms of biology and disease. Areas of active investigation include genetic and epigenetic regulation of development, molecular genetics, genomics and cell biology of stem cells, the biochemistry of micro RNA production and their regulation of gene expression, and genetic and genomic analysis of diseases in model systems and humans including cancer, cardiovascular and kidney disease, neurodegeneration and regeneration, and neuropsychiatric disease. Members of the Department have also been at the forefront of technology development in the use of new methods for genetic analysis, including new methods for engineering mutations as well as new methods for production and analysis of large genomic data sets.
The Department sponsors a graduate program leading to the PhD in the areas of molecular genetics and genomics, development, and stem cell biology. Admission to the Graduate Program is through the Combined Programs in Biological and Biomedical Sciences (BBS).
In addition to these basic science efforts, the Department is also responsible for providing clinical care in Medical Genetics in the Yale New Haven Health System. Clinical genetics services include inpatient consultation and care, general, subspecialty, cancer and prenatal genetics clinics, and clinical laboratories for cytogenetics, DNA diagnostics, and biochemical diagnostics. The Department sponsors a Medical Genetics Residency program leading to certification by the American Board of Medical Genetics. Admission to the Genetics Residency is directly through the Department.
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Genetics,chromosomeCreated and produced by QA International. QA International, 2010. All rights reserved. http://www.qa-international.comstudy of heredity in general and of genes in particular. Genetics forms one of the central pillars of biology and overlaps with many other areas such as agriculture, medicine, and biotechnology.
Since the dawn of civilization, humankind has recognized the influence of heredity and has applied its principles to the improvement of cultivated crops and domestic animals. A Babylonian tablet more than 6,000 years old, for example, shows pedigrees of horses and indicates possible inherited characteristics. Other old carvings show cross-pollination of date palm trees. Most of the mechanisms of heredity, however, remained a mystery until the 19th century, when genetics as a systematic science began.
Crick, Francis Harry Compton: proposed DNA structureEncyclopdia Britannica, Inc.Genetics arose out of the identification of genes, the fundamental units responsible for heredity. Genetics may be defined as the study of genes at all levels, including the ways in which they act in the cell and the ways in which they are transmitted from parents to offspring. Modern genetics focuses on the chemical substance that genes are made of, called deoxyribonucleic acid, or DNA, and the ways in which it affects the chemical reactions that constitute the living processes within the cell. Gene action depends on interaction with the environment. Green plants, for example, have genes containing the information necessary to synthesize the photosynthetic pigment chlorophyll that gives them their green colour. Chlorophyll is synthesized in an environment containing light because the gene for chlorophyll is expressed only when it interacts with light. If a plant is placed in a dark environment, chlorophyll synthesis stops because the gene is no longer expressed.
Genetics as a scientific discipline stemmed from the work of Gregor Mendel in the middle of the 19th century. Mendel suspected that traits were inherited as discrete units, and, although he knew nothing of the physical or chemical nature of genes at the time, his units became the basis for the development of the present understanding of heredity. All present research in genetics can be traced back to Mendels discovery of the laws governing the inheritance of traits. The word genetics was introduced in 1905 by English biologist William Bateson, who was one of the discoverers of Mendels work and who became a champion of Mendels principles of inheritance.
Although scientific evidence for patterns of genetic inheritance did not appear until Mendels work, history shows that humankind must have been interested in heredity long before the dawn of civilization. Curiosity must first have been based on human family resemblances, such as similarity in body structure, voice, gait, and gestures. Such notions were instrumental in the establishment of family and royal dynasties. Early nomadic tribes were interested in the qualities of the animals that they herded and domesticated and, undoubtedly, bred selectively. The first human settlements that practiced farming appear to have selected crop plants with favourable qualities. Ancient tomb paintings show racehorse breeding pedigrees containing clear depictions of the inheritance of several distinct physical traits in the horses. Despite this interest, the first recorded speculations on heredity did not exist until the time of the ancient Greeks; some aspects of their ideas are still considered relevant today.
Hippocrates (c. 460c. 375 bce), known as the father of medicine, believed in the inheritance of acquired characteristics, and, to account for this, he devised the hypothesis known as pangenesis. He postulated that all organs of the body of a parent gave off invisible seeds, which were like miniaturized building components and were transmitted during sexual intercourse, reassembling themselves in the mothers womb to form a baby.
Aristotle (384322 bce) emphasized the importance of blood in heredity. He thought that the blood supplied generative material for building all parts of the adult body, and he reasoned that blood was the basis for passing on this generative power to the next generation. In fact, he believed that the males semen was purified blood and that a womans menstrual blood was her equivalent of semen. These male and female contributions united in the womb to produce a baby. The blood contained some type of hereditary essences, but he believed that the baby would develop under the influence of these essences, rather than being built from the essences themselves.
Aristotles ideas about the role of blood in procreation were probably the origin of the still prevalent notion that somehow the blood is involved in heredity. Today people still speak of certain traits as being in the blood and of blood lines and blood ties. The Greek model of inheritance, in which a teeming multitude of substances was invoked, differed from that of the Mendelian model. Mendels idea was that distinct differences between individuals are determined by differences in single yet powerful hereditary factors. These single hereditary factors were identified as genes. Copies of genes are transmitted through sperm and egg and guide the development of the offspring. Genes are also responsible for reproducing the distinct features of both parents that are visible in their children.
In the two millennia between the lives of Aristotle and Mendel, few new ideas were recorded on the nature of heredity. In the 17th and 18th centuries the idea of preformation was introduced. Scientists using the newly developed microscopes imagined that they could see miniature replicas of human beings inside sperm heads. French biologist Jean-Baptiste Lamarck invoked the idea of the inheritance of acquired characters, not as an explanation for heredity but as a model for evolution. He lived at a time when the fixity of species was taken for granted, yet he maintained that this fixity was only found in a constant environment. He enunciated the law of use and disuse, which states that when certain organs become specially developed as a result of some environmental need, then that state of development is hereditary and can be passed on to progeny. He believed that in this way, over many generations, giraffes could arise from deerlike animals that had to keep stretching their necks to reach high leaves on trees.
British naturalist Alfred Russel Wallace originally postulated the theory of evolution by natural selection. However, Charles Darwins observations during his circumnavigation of the globe aboard the HMS Beagle (183136) provided evidence for natural selection and his suggestion that humans and animals shared a common ancestry. Many scientists at the time believed in a hereditary mechanism that was a version of the ancient Greek idea of pangenesis, and Darwins ideas did not appear to fit with the theory of heredity that sprang from the experiments of Mendel.
Before Gregor Mendel, theories for a hereditary mechanism were based largely on logic and speculation, not on experimentation. In his monastery garden, Mendel carried out a large number of cross-pollination experiments between variants of the garden pea, which he obtained as pure-breeding lines. He crossed peas with yellow seeds to those with green seeds and observed that the progeny seeds (the first generation, F1) were all yellow. When the F1 individuals were self-pollinated or crossed among themselves, their progeny (F2) showed a ratio of 3:1 (3/4 yellow and 1/4 green). He deduced that, since the F2 generation contained some green individuals, the determinants of greenness must have been present in the F1 generation, although they were not expressed because yellow is dominant over green. From the precise mathematical 3:1 ratio (of which he found several other examples), he deduced not only the existence of discrete hereditary units (genes) but also that the units were present in pairs in the pea plant and that the pairs separated during gamete formation. Hence, the two original lines of pea plants were proposed to be YY (yellow) and yy (green). The gametes from these were Y and y, thereby producing an F1 generation of Yy that were yellow in colour because of the dominance of Y. In the F1 generation, half the gametes were Y and the other half were y, making the F2 generation produced from random mating 1/4 Yy, 1/2 YY, and 1/4 yy, thus explaining the 3:1 ratio. The forms of the pea colour genes, Y and y, are called alleles.
Mendel also analyzed pure lines that differed in pairs of characters, such as seed colour (yellow versus green) and seed shape (round versus wrinkled). The cross of yellow round seeds with green wrinkled seeds resulted in an F1 generation that were all yellow and round, revealing the dominance of the yellow and round traits. However, the F2 generation produced by self-pollination of F1 plants showed a ratio of 9:3:3:1 (9/16 yellow round, 3/16 yellow wrinkled, 3/16 green round, and 1/16 green wrinkled; note that a 9:3:3:1 ratio is simply two 3:1 ratios combined). From this result and others like it, he deduced the independent assortment of separate gene pairs at gamete formation.
Mendels success can be attributed in part to his classic experimental approach. He chose his experimental organism well and performed many controlled experiments to collect data. From his results, he developed brilliant explanatory hypotheses and went on to test these hypotheses experimentally. Mendels methodology established a prototype for genetics that is still used today for gene discovery and understanding the genetic properties of inheritance.
Mendels genes were only hypothetical entities, factors that could be inferred to exist in order to explain his results. The 20th century saw tremendous strides in the development of the understanding of the nature of genes and how they function. Mendels publications lay unmentioned in the research literature until 1900, when the same conclusions were reached by several other investigators. Then there followed hundreds of papers showing Mendelian inheritance in a wide array of plants and animals, including humans. It seemed that Mendels ideas were of general validity. Many biologists noted that the inheritance of genes closely paralleled the inheritance of chromosomes during nuclear divisions, called meiosis, that occur in the cell divisions just prior to gamete formation.
heredity: sex-linked inheritance in Drosophila fliesEncyclopdia Britannica, Inc.It seemed that genes were parts of chromosomes. In 1910 this idea was strengthened through the demonstration of parallel inheritance of certain Drosophila (a type of fruit fly) genes on sex-determining chromosomes by American zoologist and geneticist Thomas Hunt Morgan. Morgan and one of his students, Alfred Henry Sturtevant, showed not only that certain genes seemed to be linked on the same chromosome but that the distance between genes on the same chromosome could be calculated by measuring the frequency at which new chromosomal combinations arose (these were proposed to be caused by chromosomal breakage and reunion, also known as crossing over). In 1916 another student of Morgans, Calvin Bridges, used fruit flies with an extra chromosome to prove beyond reasonable doubt that the only way to explain the abnormal inheritance of certain genes was if they were part of the extra chromosome. American geneticist Hermann Joseph Mller showed that new alleles (called mutations) could be produced at high frequencies by treating cells with X-rays, the first demonstration of an environmental mutagenic agent (mutations can also arise spontaneously). In 1931 American botanist Harriet Creighton and American scientist Barbara McClintock demonstrated that new allelic combinations of linked genes were correlated with physically exchanged chromosome parts.
In 1908 British physician Archibald Garrod proposed the important idea that the human disease alkaptonuria, and certain other hereditary diseases, were caused by inborn errors of metabolism, suggesting for the first time that linked genes had molecular action at the cell level. Molecular genetics did not begin in earnest until 1941 when American geneticist George Beadle and American biochemist Edward Tatum showed that the genes they were studying in the fungus Neurospora crassa acted by coding for catalytic proteins called enzymes. Subsequent studies in other organisms extended this idea to show that genes generally code for proteins. Soon afterward, American bacteriologist Oswald Avery, Canadian American geneticist Colin M. MacLeod, and American biologist Maclyn McCarty showed that bacterial genes are made of DNA, a finding that was later extended to all organisms.
DNAEncyclopdia Britannica, Inc.A major landmark was attained in 1953 when American geneticist and biophysicist James D. Watson and British biophysicists Francis Crick and Maurice Wilkins devised a double helix model for DNA structure. This model showed that DNA was capable of self-replication by separating its complementary strands and using them as templates for the synthesis of new DNA molecules. Each of the intertwined strands of DNA was proposed to be a chain of chemical groups called nucleotides, of which there were known to be four types. Because proteins are strings of amino acids, it was proposed that a specific nucleotide sequence of DNA could contain a code for an amino acid sequence and hence protein structure. In 1955 American molecular biologist Seymour Benzer, extending earlier studies in Drosophila, showed that the mutant sites within a gene could be mapped in relation to each other. His linear map indicated that the gene itself is a linear structure.
In 1958 the strand-separation method for DNA replication (called the semiconservative method) was demonstrated experimentally for the first time by American molecular biologist Matthew Meselson and American geneticist Franklin W. Stahl. In 1961 Crick and South African biologist Sydney Brenner showed that the genetic code must be read in triplets of nucleotides, called codons. American geneticist Charles Yanofsky showed that the positions of mutant sites within a gene matched perfectly the positions of altered amino acids in the amino acid sequence of the corresponding protein. In 1966 the complete genetic code of all 64 possible triplet coding units (codons), and the specific amino acids they code for, was deduced by American biochemists Marshall Nirenberg and Har Gobind Khorana. Subsequent studies in many organisms showed that the double helical structure of DNA, the mode of its replication, and the genetic code are the same in virtually all organisms, including plants, animals, fungi, bacteria, and viruses. In 1961 French biologist Franois Jacob and French biochemist Jacques Monod established the prototypical model for gene regulation by showing that bacterial genes can be turned on (initiating transcription into RNA and protein synthesis) and off through the binding action of regulatory proteins to a region just upstream of the coding region of the gene.
Technical advances have played an important role in the advance of genetic understanding. In 1970 American microbiologists Daniel Nathans and Hamilton Othanel Smith discovered a specialized class of enzymes (called restriction enzymes) that cut DNA at specific nucleotide target sequences. That discovery allowed American biochemist Paul Berg in 1972 to make the first artificial recombinant DNA molecule by isolating DNA molecules from different sources, cutting them, and joining them together in a test tube. These advances allowed individual genes to be cloned (amplified to a high copy number) by splicing them into self-replicating DNA molecules, such as plasmids (extragenomic circular DNA elements) or viruses, and inserting these into living bacterial cells. From these methodologies arose the field of recombinant DNA technology that presently dominates molecular genetics. In 1977 two different methods were invented for determining the nucleotide sequence of DNA: one by American molecular biologists Allan Maxam and Walter Gilbert and the other by English biochemist Fred Sanger. Such technologies made it possible to examine the structure of genes directly by nucleotide sequencing, resulting in the confirmation of many of the inferences about genes originally made indirectly.
DNA fingerprinting: polymerase chain reactionEncyclopdia Britannica, Inc.In the 1970s Canadian biochemist Michael Smith revolutionized the art of redesigning genes by devising a method for inducing specifically tailored mutations at defined sites within a gene, creating a technique known as site-directed mutagenesis. In 1983 American biochemist Kary B. Mullis invented the polymerase chain reaction, a method for rapidly detecting and amplifying a specific DNA sequence without cloning it. In the last decade of the 20th century, progress in recombinant DNA technology and in the development of automated sequencing machines led to the elucidation of complete DNA sequences of several viruses, bacteria, plants, and animals. In 2001 the complete sequence of human DNA, approximately three billion nucleotide pairs, was made public.
A time line of important milestones in the history of genetics is provided in the table.
Time line of important milestones in the history of genetics
Classical genetics, which remains the foundation for all other areas in genetics, is concerned primarily with the method by which genetic traitsclassified as dominant (always expressed), recessive (subordinate to a dominant trait), intermediate (partially expressed), or polygenic (due to multiple genes)are transmitted in plants and animals. These traits may be sex-linked (resulting from the action of a gene on the sex, or X, chromosome) or autosomal (resulting from the action of a gene on a chromosome other than a sex chromosome). Classical genetics began with Mendels study of inheritance in garden peas and continues with studies of inheritance in many different plants and animals. Today a prime reason for performing classical genetics is for gene discoverythe finding and assembling of a set of genes that affects a biological property of interest.
Cytogenetics, the microscopic study of chromosomes, blends the skills of cytologists, who study the structure and activities of cells, with those of geneticists, who study genes. Cytologists discovered chromosomes and the way in which they duplicate and separate during cell division at about the same time that geneticists began to understand the behaviour of genes at the cellular level. The close correlation between the two disciplines led to their combination.
Plant cytogenetics early became an important subdivision of cytogenetics because, as a general rule, plant chromosomes are larger than those of animals. Animal cytogenetics became important after the development of the so-called squash technique, in which entire cells are pressed flat on a piece of glass and observed through a microscope; the human chromosomes were numbered using this technique.
Today there are multiple ways to attach molecular labels to specific genes and chromosomes, as well as to specific RNAs and proteins, that make these molecules easily discernible from other components of cells, thereby greatly facilitating cytogenetics research.
Microorganisms were generally ignored by the early geneticists because they are small in size and were thought to lack variable traits and the sexual reproduction necessary for a mixing of genes from different organisms. After it was discovered that microorganisms have many different physical and physiological characteristics that are amenable to study, they became objects of great interest to geneticists because of their small size and the fact that they reproduce much more rapidly than larger organisms. Bacteria became important model organisms in genetic analysis, and many discoveries of general interest in genetics arose from their study. Bacterial genetics is the centre of cloning technology.
Viral genetics is another key part of microbial genetics. The genetics of viruses that attack bacteria were the first to be elucidated. Since then, studies and findings of viral genetics have been applied to viruses pathogenic on plants and animals, including humans. Viruses are also used as vectors (agents that carry and introduce modified genetic material into an organism) in DNA technology.
Molecular genetics is the study of the molecular structure of DNA, its cellular activities (including its replication), and its influence in determining the overall makeup of an organism. Molecular genetics relies heavily on genetic engineering (recombinant DNA technology), which can be used to modify organisms by adding foreign DNA, thereby forming transgenic organisms. Since the early 1980s, these techniques have been used extensively in basic biological research and are also fundamental to the biotechnology industry, which is devoted to the manufacture of agricultural and medical products. Transgenesis forms the basis of gene therapy, the attempt to cure genetic disease by addition of normally functioning genes from exogenous sources.
The development of the technology to sequence the DNA of whole genomes on a routine basis has given rise to the discipline of genomics, which dominates genetics research today. Genomics is the study of the structure, function, and evolutionary comparison of whole genomes. Genomics has made it possible to study gene function at a broader level, revealing sets of genes that interact to impinge on some biological property of interest to the researcher. Bioinformatics is the computer-based discipline that deals with the analysis of such large sets of biological information, especially as it applies to genomic information.
The study of genes in populations of animals, plants, and microbes provides information on past migrations, evolutionary relationships and extents of mixing among different varieties and species, and methods of adaptation to the environment. Statistical methods are used to analyze gene distributions and chromosomal variations in populations.
Population genetics is based on the mathematics of the frequencies of alleles and of genetic types in populations. For example, the Hardy-Weinberg formula, p2 + 2pq + q2 = 1, predicts the frequency of individuals with the respective homozygous dominant (AA), heterozygous (Aa), and homozygous recessive (aa) genotypes in a randomly mating population. Selection, mutation, and random changes can be incorporated into such mathematical models to explain and predict the course of evolutionary change at the population level. These methods can be used on alleles of known phenotypic effect, such as the recessive allele for albinism, or on DNA segments of any type of known or unknown function.
Human population geneticists have traced the origins and migration and invasion routes of modern humans, Homo sapiens. DNA comparisons between the present peoples on the planet have pointed to an African origin of Homo sapiens. Tracing specific forms of genes has allowed geneticists to deduce probable migration routes out of Africa to the areas colonized today. Similar studies show to what degree present populations have been mixed by recent patterns of travel.
Another aspect of genetics is the study of the influence of heredity on behaviour. Many aspects of animal behaviour are genetically determined and can therefore be treated as similar to other biological properties. This is the subject material of behaviour genetics, whose goal is to determine which genes control various aspects of behaviour in animals. Human behaviour is difficult to analyze because of the powerful effects of environmental factors, such as culture. Few cases of genetic determination of complex human behaviour are known. Genomics studies provide a useful way to explore the genetic factors involved in complex human traits such as behaviour.
Some geneticists specialize in the hereditary processes of human genetics. Most of the emphasis is on understanding and treating genetic disease and genetically influenced ill health, areas collectively known as medical genetics. One broad area of activity is laboratory research dealing with the mechanisms of human gene function and malfunction and investigating pharmaceutical and other types of treatments. Since there is a high degree of evolutionary conservation between organisms, research on model organismssuch as bacteria, fungi, and fruit flies (Drosophila)which are easier to study, often provides important insights into human gene function.
Many single-gene diseases, caused by mutant alleles of a single gene, have been discovered. Two well-characterized single-gene diseases include phenylketonuria (PKU) and Tay-Sachs disease. Other diseases, such as heart disease, schizophrenia, and depression, are thought to have more complex heredity components that involve a number of different genes. These diseases are the focus of a great deal of research that is being carried out today.
Another broad area of activity is clinical genetics, which centres on advising parents of the likelihood of their children being affected by genetic disease caused by mutant genes and abnormal chromosome structure and number. Such genetic counseling is based on examining individual and family medical records and on diagnostic procedures that can detect unexpressed, abnormal forms of genes. Counseling is carried out by physicians with a particular interest in this area or by specially trained nonphysicians.
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Genetics
Background:
Homunculus in Sperm One question that has always intrigued us humans is Where did we come from? Long ago, Hippocrates and Aristotle proposed the idea of what they called pangenes, which they thought were tiny pieces of body parts. They thought that pangenes came together to make up the homunculus, a tiny pre-formed human that people thought grew into a baby. In the 1600s, the development of the microscope brought the discovery of eggs and sperm. Antonie van Leeuwenhoek, using a primitive microscope, thought he saw the homunculus curled up in a sperm cell. His followers believed that the homunculus was in the sperm, the father planted his seed, and the mother just incubated and nourished the homunculus so it grew into a baby. On the other hand, Regnier de Graaf and his followers thought that they saw the homunculus in the egg, and the presence of semen just somehow stimulated its growth. In the 1800s, a very novel, radical idea arose: both parents contribute to the new baby, but people (even Darwin, as he proposed his theory) still believed that these contributions were in the form of pangenes.
Modern genetics traces its beginnings to Gregor Mendel, an Austrian monk, who grew peas in a monastery garden. Mendel was unique among biologists of his time because he sought quantifiable data, and actually counted the results of his crosses. He published his findings in 1865, but at that time, people didnt know about mitosis and meiosis, so his conclusions seemed unbelievable, and his work was ignored until it was rediscovered in 1900 by a couple of botanists who were doing research on something else. Peas are an ideal organism for this type of research because they are easy to grow and it is easy to control mating.
We will be looking at the sorts of genetic crosses Mendel did, but first, it is necessary to introduce some terminology:
Monohybrid Cross and Probabilities:
A monohybrid cross is a genetic cross where only one gene/trait is being studied. P stands for the parental generation, while F1 and F2 stand for the first filial generation (the children) and second filial generation (the grandchildren). Each parent can give one chromosome of each pair, therefore one allele for each trait, to the offspring. Thus, when figuring out what kind(s) of gametes an individual can produce, it is necessary to choose one of the two alleles for each gene (which presents no problem if they are the same).
Purple Pea Flower White Pea Flower For example, a true-breeding purple-flowered plant (the dominant allele for this gene) would have the genotype PP, and be able to make gametes with either P or P alleles. A true-breeding white-flowered plant (the recessive allele for this gene) would have the genotype pp, and be able to make gametes with either p or p alleles. Note that both of these parent plants would be homozygous. If one gamete from each of these parents got together to form a new plant, that plant would receive a P allele from one parent and a p allele from the other parent, thus all of the F1 generation will be genotype Pp, they will be heterozygous, and since purple is dominant, they will look purple. What if two individuals from the F1 generation are crossed with each other (PpPp)? Since gametes contain one allele for each gene under consideration, each of these individuals could contribute either a P or a p in his/her gametes. Each of these gametes from each parent could pair with each from the other, thus yielding a number of possible combinations for the offspring. We need a way, then, to predict what the possible offspring might be. Actually, there are two ways of doing this. The first is to do a Punnett square (named after Reginald Crandall Punnett). The possible eggs from the female are listed down the left side, and there is one row for each possible egg. The possible sperm from the male are listed across the top, and there is one column for each possible sperm. The boxes at the intersections of these rows and columns show the possible offspring resulting from that sperm fertilizing that egg. The Punnett square from this cross would look like this:
Note that the chance of having a gamete with a P allele is and the chance of a gamete with a p allele is , so the chance of an egg with P and a sperm with P getting together to form an offspring that is PP is =, just like the probabilities involved tossing coins. Thus, the possible offspring include: PP, ( Pp + pP, which are the same (Pp), since P is dominant over p), so = Pp, and pp.
Another way to calculate this is to use a branching, tree diagram:
Note, again, that the chance of Pp is +=. A shorter way of telling how many PP, Pp, and pp could be expected, would be to say that there is a 1:2:1 genotype ratio (that comes from the , , and , above, and by the way, notice that they add up to , so we know we have accounted for everything). The chance of getting at least one dominant allele (either PP or Pp) necessary for purple color (this can be written as P) is +=, so we could say that theres a 3:1 phenotype ratio. These two ratios are classic genotype and phenotype ratios for a monohybrid cross between two heterozygotes.
Mendels Four-Part Theory:
Based on his data, Mendel came up with a four-part theory of how genetics works:
Some special cases:
(Rh factor, by the way, is a totally separate gene with Rh+ [R] and Rh [r] alleles [actually, that gene also has multiple alleles, but the vast majority of people are positive or negative for one particular allele called D]. In the U. S., about 85% of the population is Rh+ [RR and Rr] and 15% Rh [rr], thus the chances of someone being O [having both ii and rr] would be 45% 15% = 6.75%. The rarest blood type in the U. S. would be AB, about 0.45% of the population.]
This is a cross where two traits/genes are under consideration. For example, in peas if R = round, so r = wrinkled, and Y = yellow, so y = green, in a cross between RRYY rryy, the gametes must have ONE ALLELE FOR EACH GENE, so in this case, RRYY could produce gametes with one R AND one Y, or RY, and rryy could produce gametes with one r AND one y, or ry. The F1 would get RY from one parent and ry from the other, thus would all be RrYy. Note that it is necessary to keep the alleles for the same gene together and put the dominant allele (capital letter) first for EACH GENE. In calculating what the F2 generation would be, you must first figure out what gametes (eggs or sperm) each parent can make. It is very important to remember that gametes must have ONE ALLELE FOR EACH GENE, so figure out the possibilities this way:
Thus, each parent could make four kinds of gametes, so the Punnett square would be 44 cells.
This would give the following possible offspring:
Thus the genotype ratio is 1:2:1:2:4:2:1:2:1 and the phenotype ratio is 9:3:3:1. Notice the shorthand used to represent the phenotypes. Since both RR and Rr will look round, rather than writing round pea seeds, we can use R to say its got at least one R, so itll be round.
Try This:
On your own, try IAiRr IBiRr, a cross involving both the ABO blood group and Rh factor. Note, a little later, we will discuss what those blood groups actually are/do.
Genotype and Phenotype Are Not the Same:
It is important to understand the difference between genotype and phenotype. For example, for most of the genes we will be discussing, an organism with the genotype of, say, BB and an organism who is Bb both have at least one dominant allele for that gene, and thus, would both express/show/be the dominant phenotype. If, for example, this was a gene for human eye color, then B would represent the dominant allele which codes for make brown eyes, and b would represent the recessive allele which codes for blue eyes (technically, more like, we dont know how to make brown, so blue is the default). Thus, people whose genotypes are either BB or Bb both have instructions for make brown, so the phenotypes of both are brown eye color.
As another example where many people get confused, an individuals sex is a phenotype, not a genotype! We can talk of a person as having either two X chromosomes (XX) or one X and one Y chromosome (XY). Those are, essentially, genotypes, and there are also a few people who have genotypes such as X (also called XO), XXX, or XXY. Those X and Y chromosomes contain/consist of a number of genes, and factors such as what alleles a person has for each of those genes, how those alleles are expressed, and how that gene expression affects/influences various body processes will all come together to produce that phenotype which we call a persons sex. In humans, if all those alleles are expressed in what we like to think of as being normal, then, usually, X, XX, and XXX are expressed as a female phenotype (with X and XXX producing some other physical characteristics considered to be typical for those genotypes), while the result of how the XY combination is expressed usually results in what we refer to as a male phenotype.
However, while uncommon, it is entirely possible that due to a mutation in some gene, somewhere, that codes for some enzyme or hormone, a person with 2 X chromosomes (XX) can have a male phenotype; can, clearly and unambiguously, be male. Similarly, while also not very common, it is also possible, due to a mutation in some gene, somewhere, that codes for some hormone or enzyme, that a person with an X and a Y chromosome (XY) can have a female phenotype; can, clearly and unambiguously, be female. Interestingly, because of differences in how the genes/alleles are expressed, the XXY combination typically results in a male in humans but results in a female in fruit flies.
Our culture, our way of thinking, is so locked into having/needing to choose between male and female as the only two options, that while in the unambiguous cases just mentioned where a persons expressed phenotype obviously fits our preconception of maleness or femaleness even if their genotype/chromosomes are different from what we might think (and of which we would not even be aware unless we were that persons doctor and maybe not even then), on the other hand, people whose bodies dont exactly and neatly fit into one of those two categories are lumped together in a group and labeled as intersex. Typically, at birth, their parents are advised by medical personnel to choose whether they wish to bring this child up as a boy or a girl, and may even be pressured into having cosmetic surgery performed on the child to make the child look more like the chosen sex assignment, yet it frequently happens as the child grows up, due to the influence of internal factors such as hormones, etc., that he or she does not feel like the sex which the doctors assigned/labeled at birth. On the other hand, if parents try to be more neutral and let the child make that choice when and if the child decides to do so, that tends to expose the child to a lot of ridicule from classmates and even other adults.
Pedigrees:
Sample Pedigree In pedigrees, a circle represents a female and a square represents a male. Filled-in vs. open symbols are used to distinguish between two phenotypes for the gene in question, and a half-filled symbol may be used to designate a carrier (a heterozygous individual who has a recessive allele for some gene, but is not showing that phenotype). Here is a sample pedigree for eye color. If the people with filled-in (dark) symbols have brown eyes and those with open (light) symbols have blue eyes, can you figure out the genotypes of the people marked with *?
Genetic Basis of Behavior, Polyploids:
Some further notes on genetics: We tend to think of genes that control what an organism looks like, etc., but genes can also control behavior of animals. For example, bird songs and other courtship rituals are under genetic control. The most successful competitors live and mate and pass on their genes. On a different subject, many of our horticultural plant varieties are polyploid plants. Typically, like us, plants are diploid. Horticulturists have figured out ways to manipulate plants and make triploid or tetraploid plants. Typically these plants are larger and/or have bigger or more ruffled flowers and/or larger seeds. While triploid plants are usually sterile (with three sets of chromosomes they have trouble doing meiosis), tetraploid plants are usually fertile and can reproduce. I believe I read somewhere that the wheat we eat is actually a hexaploid, resulting in seeds that are quite a bit larger than its grass-like ancestor.
References:
Borror, Donald J. 1960. Dictionary of Root Words and Combining Forms. Mayfield Publ. Co.
Campbell, Neil A., Lawrence G. Mitchell, Jane B. Reece. 1999. Biology, 5th Ed. Benjamin/Cummings Publ. Co., Inc. Menlo Park, CA. (plus earlier editions)
Campbell, Neil A., Lawrence G. Mitchell, Jane B. Reece. 1999. Biology: Concepts and Connections, 3rd Ed. Benjamin/Cummings Publ. Co., Inc. Menlo Park, CA. (plus earlier editions)
Marchuk, William N. 1992. A Life Science Lexicon. Wm. C. Brown Publishers, Dubuque, IA.
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Genetics
(Science: study) The study of the patterns of inheritance of specific traits. Relating to genes and genetic information. Also known as heredity. Modern theories explain how traits are passed down from parent to offspring. The first to test this theory was gregor mendel, a monk from Austria who tried to explain why some pea plants were short and some were tall, but none were in between. He placed nets over the plants so no bees or flies could pollinate the plants. Pea plants are one of the few plants capable of self pollination, so Mendel tried this with short plants and all were short, so he expected that the same thing would happen with the tall plants. But when he tried it, 75% were tall and 25% were short. This was when he used a punnett Square. A punnett Square is a model used to predict the possible outcomes of offspring.
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Last update 23andMe returns with FDA-approved genetic health tests, Oct 21, 2015
Genetic ancestry, as well as facial characteristics, may play an important part in who we select as mates, according to an analysis from UC San Francisco, Microsoft Research, Harvard, UC Berkeley and Tel Aviv University.
(Medical Xpress)A large team of researchers affiliated with multiple institutions in several European countries has found new genetic variants that put heavy drinkers at higher risk of developing cirrhosis of the liver. ...
Genetic testing company 23andMe is reintroducing some health screening tools that federal regulators forced off the market more than two years ago, due to concerns about their accuracy and interpretation by customers.
Researchers at King's College London have identified a new gene linked to nerve function, which could provide a treatment target for 'switching off' the gene in people with neurodegenerative diseases such as Parkinson's disease.
Never before have scientists been able to make scores of simultaneous genetic edits to an organism's genome. But now, in a landmark study by George Church and his team at the Wyss Institute for Biologically Inspired Engineering ...
Eczema - an itchy dry-skin condition - affects an estimated one in five children and one in 12 adults in the UK. Genes play an important role in determining how likely we are to develop eczema but the majority of the genes ...
Genes involved in schizophrenia and obesity have been highlighted in a new UCL study, which could lead to a better understanding of the DNA variants which affect risk of these conditions and aid the development of improved ...
We've known for years that the Huntingtin protein (Htt) is responsible for Huntington's disease, a neurodegenerative disorder that diminishes a person's mental and physical abilities.
Using two complementary analytical approaches, scientists at Whitehead Institute and Broad Institute of MIT and Harvard have for the first time identified the universe of genes in the human genome essential for the survival ...
A coalition of leukemia researchers led by scientists from UC San Francisco has discovered surprising genetic diversity in juvenile myelomonocytic leukemia (JMML), a rare but aggressive childhood blood cancer.
The proposed Regulation on In Vitro Diagnostic Medical Devices (IVDs) negotiations, currently at the stage of tripartite negotiations between the Council (representing Member State governments), the European Parliament, and ...
In the kidney, injured cells can be kicked into reparative mode by a gene called Sox9, according to a new paper published in Cell Reports.
University of Otago researchers working with zebrafish have published a study providing new insights into the causes of the congenital heart defects associated with a rare developmental disorder.
The team behind the Deciphering Developmental Disorders (DDD) Study, one of the world's largest nationwide rare disease genome-wide sequencing initiatives, have developed a novel computational approach to identify genetic ...
The whimsically named sonic hedgehog gene, best known for controlling embryonic development, also maintains the normal physiological state and repair process of an adult healthy lung, if damaged, according to new research ...
A research group at Tohoku Medical Megabank Organization (ToMMo) has successfully constructed a Japanese population reference panel (1KJPN), from the genome information of 1,070 individuals who had participated in the cohort ...
Walt Whitman's famous line, "I am large, I contain multitudes," has gained a new level of biological relevance.
Research indicates for the first time that mutations within the DNA sequence of mitochondria impact on the energy producing capacity of these cells, with significant effects on fertility and life expectancy - and remarkably ...
A new test detects virtually any virus that infects people and animals, according to research at Washington University School of Medicine in St. Louis, where the technology was developed.
An international team of scientists from the 1000 Genomes Project Consortium has created the world's largest catalog of genomic differences among humans, providing researchers with powerful clues to help them establish why ...
Scientists have calculated more precise measurements of heritabilitythe influence of underlying genesin nine autoimmune diseases that begin in childhood. The research may strengthen researchers' abilities to better ...
Published today in Nature, the findings detail a new gene locus that can explain why, in communities where everyone is constantly exposed to malaria, some children develop severe malaria and others don't. Now, researchers ...
In recent years, University of Utah biologists showed that when wild-type mice compete in seminatural "mouse barns" for food, territory and mates, they can suffer health problems not revealed by conventional toxicity tests ...
An international study of nearly 70,000 women has identified more than forty regions of the human genome that are involved in governing at what age a woman goes through the menopause. The study, led by scientists at the Universities ...
Cells of multicellular organisms contain identical genetic material (the genome) yet can have drastic differences in their structural arrangements and functions. This variation of the distinct cell types comes from the differential ...
Using a genome-wide association study, EPFL scientists have identified subtle genetic changes that can cause substantial differences to how we fight viral infections.
Mitochondria are not only the power plants of our cells, these tiny structures also play a central role in our physiology. Furthermore, by enabling flexible physiological responses to new environments, mitochondria have helped ...
A genetic variant near the KLF14 gene regulates hundreds of genes that govern how and where women's bodies store fat, which affects their risk of developing Type 2 diabetes, according to research presented at the American ...
Progeria, a premature aging disease, is the research focus of Roland Foisner's team at the Max F. Perutz Laboratories of the University of Vienna and the Medical University of Vienna. Children suffering from progeria die ...
Tourists spending a recuperative holiday on the Italian coast may be envious of the regenerative abilities of locally found flatworm Macrostomum lignano. Named for its discovery near the Italian beach town of Lignano Sabbiadoro, ...
Some research has suggested that omega-3 fatty acids, abundant in fish oils, can relieve inflammation in Crohn's disease. But a new study using software developed by Duke scientists hints that we should be paying closer attention ...
A 'gene signature' that could be used to predict the onset of diseases, such as Alzheimer's, years in advance has been developed in research published in the open access journal Genome Biology.
An international team of scientists led from Sweden's Karolinska Institutet has for the first time mapped all the genes that are activated in the first few days of a fertilized human egg. The study, which is being published ...
A single stem cell has the potential to generate an animal made of millions of different types of cells. Some cancers contain stem-like but abnormal cells that can act like mini factories to rapidly churn out not only more ...
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Genetics News - Genetics Science, Genetics Technology, Genetics
10/09/2015
RESEARCH ARTICLE
New emerging pathogens are a significant threat to human health. Lisa Gralinksi and colleagues discover new animal models that better capture the range of disease found in human SARS patients and also find four novel susceptibility loci governing various aspects of SARS-induced pathogenesis.
10/09/2015
RESEARCH ARTICLE
Jingyan Liu and colleagues identify and characterize ibr5-7, a mutant that suppresses the chilling-induced defense responses of chs3-1. They observe that the enhanced defense responses and cell death in the chs3-1 mutant are synergistically dependent on IBR5 and HSP90.
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History of the Department
On the following page is a brief history of the department, along with a video entitled The First 48 Years of the Department of Genetics at the University of Pennsylvania. On the subsequent page there are four additional videos: The Billingham Chairmanship and Transplantation Immunology (Clyde Barker and David Gasser), The Mellman Chairmanship and Cytogenetics (Beverly Emanuel and David Gasser), The Mellman Chairmanship and Maternal/Fetal Medicine (Michael Mennuti and David Gasser), and The Kazazian Chairmanship (Haig Kazazian and David Gasser). Read and view more about the department...
The Department of Genetics hosts a different speaker every Monday of the academic year, with invitees ranging from postdoctoral researchers to prominent scientists presenting a broad array of current, genetics-related research. Our series is cosponsored with the Department of Cell and Developmental Biology and the Institute for Regenerative Medicine. Click here to view the schedule.
Congratulations to Dr. Janine Lamonica from the Zhou lab for receiving a two-year postdoctoral fellowship from the International Rett Syndrome Foundation!
We are pleased to announce that this year's Tom Kadesch Prize in Genetic Research has been awarded to Judy I-Ting Wang. Read more about Ms. Wang, the Kadesch Prize, and the Symposium...
Zhaolan Zhou, Dan Rader, Judy Wang, Alex Kadesch, Becca Mueller
We are pleased to announce the recruitment of Golnaz Vahedi, Ph.D.Golnaz received her Ph.D. in Computational Biology from Texas A&M in 2009, where she studied gene regulatory networks applying Boolean probabilistic modeling and other methods. After developing her interest in regulatory networks controlling gene expression, Golnaz joined Dr. John OSheas laboratory at the National Institutes of Health in 2009. During her postdoctoral training Dr. Vahedi made seminal findings in the area of epigenetic and transcription factor control of cell fate in the immune system. Golnaz will join the Department as a tenure track Assistant Professor on May 1, 2015. Her arrival is expected to further strengthen and expand the Department's capacities in the computational and bioinformatics aspects of immunogenetics.
Yoseph Barash In silico to in vivo splicing analysis using splicing code models. Gazzara MR, Vaquero-Garcia J, Lynch KW, Barash Y. Methods. S1046-2023(13)00444-1, 2013.
AVISPA: a web tool for the prediction and analysis of alternative splicing. Barash Y, Vaquero-Garcia J, Gonzlez-Vallinas J, Xiong HY, Gao W, Lee LJ, Frey BJ. Genome Biol. 14(10):R114, 2013.
Maja Bucan From Mouse to Human: Evolutionary Genomics Analysis of Human Orthologs of Essential Genes. Georgi B, Voight BF, Bucan M PLoS Genet. 2013. 9(5): e1003484.
Genomic View of Bipolar Disorder Revealed by Whole Genome Sequencing in a Genetic Isolate Georgi B, Craig D, Kember RL, Liu W, Lindquist I, Nasser S, Brown C, Egeland JA, Paul SM, Bucan M PLoS Genet 10(3): e1004229. doi:10.1371/journal.pgen.1004229, 2014.
Doug Epstein Divergent roles for Wnt/-catenin signaling in epithelial maintenance and breakdown during semicircular canal formation. Rakowiecki S,Epstein DJ. Development 140(8):1730-9, 2013.
Inhibition of Sox2-dependent activation of Shh in the ventral diencephalon by Tbx3 is required for formation of the neurohypophysis. Trowe MO, Zhao L, Weiss AC, Christoffels V,Epstein DJ, Kispert A. Development 140(11):2299-309, 2013.
Arupa Ganguly Parental nutrient intake and risk of retinoblastoma resulting from new germline RB1 mutation. Bunin GR, Li Y, Ganguly A, Meadows AT, Tseng M. Cancer Causes Control. 2013 Feb;24(2):343-55. doi: 10.1007/s10552-012-0120-x. Epub 2012 Dec 8.
A case-control study of paternal occupational exposures and the risk of childhood sporadic bilateral retinoblastoma. Abdolahi A, van Wijngaarden E, McClean MD, Herrick RF, Allen JG, Ganguly A, Bunin GR. Occup Environ Med. 2013 Jun;70(6):372-9. doi: 10.1136/oemed-2012-101062. Epub 2013 Mar 16.
Genomic profile of 320 uveal melanoma cases: chromosome 8p-loss and metastatic outcome. Ewens KG, Kanetsky PA, Richards-Yutz J, Al-Dahmash S, De Luca MC, Bianciotto CG, Shields CL, Ganguly A. Invest Ophthalmol Vis Sci. 2013 Aug 23;54(8):5721-9. doi: 10.1167/iovs.13-12195.
Dominant form of congenital hyperinsulinism maps to HK1 region on 10q. Pinney SE, Ganapathy K, Bradfield J, Stokes D, Sasson A, Mackiewicz K, Boodhansingh K, Hughes N, Becker S, Givler S, Macmullen C, Monos D, Ganguly A, Hakonarson H, Stanley CA. Horm Res Paediatr. 2013;80(1):18-27. doi: 10.1159/000351943. Epub 2013 Jul 13.
Enhanced Sensitivity for Detection of Low-Level Germline Mosaic RB1 Mutations in Sporadic Retinoblastoma Cases Using Deep Semiconductor Sequencing. Chen Z, Moran K, Richards-Yutz J, Toorens E, Gerhart D, Ganguly T, Shields CL, Ganguly A. Hum Mutat. 2013 Nov 26. doi: 10.1002/humu.22488. [Epub ahead of print]
David Gasser Focal segmental glomerulosclerosis is associated with a PDSS2 haplotype and, independently, with a decreased content of coenzyme Q10. Gasser DL, Winkler CA, Peng M, An P, McKenzie LM, Kirk GD, Shi Y, Xie LX, Marbois BN, Clarke CF and Kopp JB. Am J Physiol Renal Physiol 305(8): F1228-F1238, 2013.
Yugong Ho An -regulatory pathway establishes the definitive chromatin conformation at the Pit-1 locus Ho Y, Cooke NE, Liebhaber SA. Mol Cell Biol. In Press.
Stephen Liebhaber An -regulatory pathway establishes the definitive chromatin conformation at the Pit-1 locus Ho Y, Cooke NE, Liebhaber SA. Mol Cell Biol. In Press.
TissueSpecific CTCF Occupancy andBoundary Function at the Human Growth HormoneLocus Tsai, Y-C, Cooke, NE, and Liebhaber, SA Nucleic Acids Research. 42: 4906-21., 2014.
Specific enrichment of the RNA-bindingproteins PCBP1 and PCBP2 in chief cells of the murinegastric mucosa Ghanem,LR, Chatterji, P, and Liebhaber, SA Gene Expression Patterns. 14:78-87, 2014. Autonomous Actions of theHumanGrowth Hormone Long-Range Enhancer Yoo, EJ, Brown, CD., Tsai, Y-C, Cooke, NE, and Liebhaber, SA Nucleic Acids Research. 2015.
Julia I-Ju Leu Structural basis for the inhibition of HSP70 and DnaK chaperones by small-molecule targeting of a C-terminal allosteric pocket. Leu JI, Zhang P, Murphy ME, Marmorstein R, George DL ACS Chem Biol. 9(11): 2508-16, 2014.
Crystal structure of the stress-inducible human heat shock protein 70 substrate-binding domain in complex with peptide substrate. Zhang P, Leu JI, Murphy ME, George DL, Marmorstein R PLoS One. 9(7): e103518, 2014.
Meera Sundaram A cell non-autonomous role for Ras signaling in C. elegans neuroblast delamination Parry, J. M. and Sundaram, M. V. Development 141: 4279-4284, 2014.
Sarah Tishkoff Higher frequency of genetic variants conferring increased risk for ADRs for commonly used drugs treating cancer, AIDS and tuberculosis in persons of African descent. Aminkeng F, Ross CJ, Rassekh SR, Brunham LR, Sistonen J, Dube MP, Ibrahim M, Nyambo TB, Omar SA, Froment A, Bodo JM, Tishkoff S, Carleton BC, Hayden MR. The Pharmacogenomics Journal J. doi: 10.1038/tpj. 2013.
Comparison Between Southern Blots and qPCR Analysis of Leukocyte Telomere Length in the Health ABC Study. Elbers CC, Garcia ME, Kimura M, Cummings SR, Nalls MA, Newman AB, Park V, Sanders JL, Tranah GJ, Tishkoff SA, Harris TB, Aviv A. The journals of gerontology. Series A, Biological sciences and medical sciences, published online ahead of print, 2013.
Patterns of nucleotide and haplotype diversity at ICAM-1 across global human populations with varying levels of malaria exposure. Gomez F, Tomas G, Ko WY, Ranciaro A, Froment A,Ibrahim M, Lema G, Nyambo TB, Omar SA, Wambebe C, Hirbo JB, Rocha J, Tishkoff SA. Human Genetics 132(9): 987-99, 2013.
Identifying Darwinian selection acting on different human APOL1 variants among diverse African populations. Ko WY, Rajan P, Gomez F,Scheinfeldt L, An P, Winkler CA, Froment A, Nyambo TB, Omar SA, Wambebe C, Ranciaro A, Hirbo JB, Tishkoff SA. American Journal of Human Genetics 93(1): 54-66, 2013.
Great ape genetic diversity and population history. Prado-Martinez J, Sudmant PH, Kidd JM, Li H, Kelley JL, Lorente-Galdos B, Veeramah KR, Woerner AE, O'Connor TD, Santpere G, Cagan A, Theunert C, Casals F, Laayouni H, Munch K, Hobolth A, Halager AE, Malig M, Hernandez-Rodriguez J, Hernando-Herraez I, Prfer K, Pybus M, Johnstone L, Lachmann M, Alkan C, Twigg D, Petit N, Baker C, Hormozdiari F, Fernandez-Callejo M, Dabad M, Wilson ML, Stevison L, Camprub C, Carvalho T, Ruiz-Herrera A, Vives L, Mele M, Abello T, Kondova I, Bontrop RE, Pusey A, Lankester F, Kiyang JA, Bergl RA, Lonsdorf E, Myers S, Ventura M, Gagneux P, Comas D, Siegismund H, Blanc J, Agueda-Calpena L, Gut M, Fulton L, Tishkoff SA, Mullikin JC, Wilson RK, Gut IG, Gonder MK, Ryder OA, Hahn BH, Navarro A, Akey JM, Bertranpetit J, Reich D, Mailund T, Schierup MH, Hvilsom C, Andrs AM, Wall JD, Bustamante CD, Hammer MF, Eichler EE, Marques-Bonet T. Nature. 499(7459):471-5. 2013. Origin and differential selection of allelic variation at TAS2R16 associated with salicin bitter taste sensitivity in Africa. Campbell MC, Ranciaro A, Zinshteyn D, Rawlings-Goss R, Hirbo JB, Thompson SI, Woldemeskel D, Froment A, Rucker JB, Omar SA, Bodo J-M, Nyambo T, Belay G, Drayna D, Breslin PAS, Tishkoff SA. Molecular Biology and Evolution, Advanced online publication. 2013.
Zhaolan (Joe) Zhou Cellular origins of auditory event-related potential deficits in Rett syndrome Goffin D, Brodkin ES, Blendy JA, Siegel SJ and Zhou Z Nature Neuroscience. 17(6): 804-806, 2014.
Yoseph Barash has been awarded an R01 from the National Institute on Aging. Title: Modeling Splicing in normal tissues and neurodegenerative disease R01 AG046544-01A1
Joe Zhou has been awarded an R01 from the NINDS. Title: Understanding the Pathogenic Mechanisms of Rett Syndrome R01-NS081054
Donna George has been awarded a P01 from the NCI. Title: Targeted Therapies in Melanoma 2P01 CA114046-06
John Murray has been awarded an R01 from the NIH. Title: Mechanisms integrating lineage history with fate specification in C. elegans 1R01GM105676-01A1
Casey Brown has been awarded an R01 from the NIMH. Title: Identification and validation of cell specific eQTLs by Bayesian modeling 1-R01-MH101822-01
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Monohybrid Cross Learn about the basic principles that govern Mendelian inheritance in plants and animals.
Dihybrid Cross Investigate the principles that govern inheritance of different traits in a dihybrid cross.
Sex-linked Inheritance 1 Understand the principles that govern inheritance of genes on sex chromosomes.
Sex-linked Inheritance 2 Explore sex-linked inheritance with a special twist--crossing over between two traits.
MendelWeb is an educational resource for teachers and students interested in the origins of classical genetics, introductory data analysis, elementary plant science, and the history and literature of science.
Electronic Scholarly Publishing (ESP) This site is dedicated to the electronic publishing of scientific and other scholarly materials. Of particular interest are the history of science, genetics, computational biology, and genome research.
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