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Topic: Genetic variation


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  Genetic Variation   (Site not responding. Last check: 2007-10-16)
Genetic variation is when the genes carried by the members of a population differ from one another (like hair or eye color).
Genetic diversity is rapidly lost in small populations because not all genes are passed from one generation to the next.
The potential for loss of genetic diversity in captive populations of endangered species is high because these captive populations are small by nature.
www.hrw.com /science/si-science/biology/animals/glt/pedigree/genev.html   (147 words)

  
 Genetic variation - Wikipedia, the free encyclopedia
Genetic variation refers to the variation in the genetic material of a population or species, and includes the nuclear, mitochodrial, ribosomal genomes as well as the genomes of other organelles.
New genetic variation is caused by genetic mutation, which may take the form of recombination, migration and/or alterations in the karyotype (the number, shape, size and internal arrangement of the chromosomes).
Genetic drift is a statistical measure of the rate of genetic variation in a population.
en.wikipedia.org /wiki/Genetic_variation   (397 words)

  
 Genetic - Understanding Human Genetic Variation, page 1
But our interest in human genetics does not stop at the boundaries of the species, for what we learn about human genetic variation and its sources and transmission inevitably contributes to our understanding of genetics in general, just as the study of variation in other species informs our understanding of our own.
By the early 1900s, cytologists had demonstrated that heredity is the consequence of the genetic continuity of cells by cell division, had identified the gametes as the vehicles that transmit genetic information from one generation to another, and had collected strong evidence for the central role of the nucleus and the chromosomes in heredity.
Analysis of human genetic variation also confirms that humans share much of their genetic information with the rest of the natural world—an indication of the relatedness of all life by descent with modification from common ancestors.
science.education.nih.gov /supplements/nih1/genetic/guide/genetic_variation1.htm   (2169 words)

  
 Introduction to Evolutionary Biology
Fitness, in an evolutionary sense, is the average reproductive output of a class of genetic variants in a gene pool.
The amount of genetic variation found in a population is the balance between the actions of these mechanisms.
Population genetics is a field of biology that attempts to measure and explain the levels of genetic variation in populations.
www.talkorigins.org /faqs/faq-intro-to-biology.html   (15764 words)

  
 Evolution, Science and Society: Some Accomplishments of Evolutionary Biology
For example, the genes that govern the first steps in embryonic development, specifying the axes and major body regions of the embryo-to-be, are similar in sequence, organization, and basic function in insects and vertebrates; in fact, some mouse genes, implanted in a fly's genome, can "instruct" the fly genes to perform their normal developmental functions.
The reservoir of genetic variation has contributed to the success of artificial selection (deliberate selection by humans) of desirable traits in crops and domestic animals, and accounts for other instances of rapid evolution, such as the development of insecticide resistance in many species of insects.
Genetic studies have shown that in some instances, this incompatibility is caused by a small number of genes, suggesting that speciation has occurred rapidly, while in other cases, interactions among a large number of genes are responsible, implying that speciation has occurred slowly and gradually.
evonet.sdsc.edu /evoscisociety/accomplim_of_eb.htm   (2606 words)

  
 genome.gov | 2002 Release: Genetic Variation Mapping Launch
Variation in a DNA base sequence - when one genetic letter is replaced by another - may similarly change the meaning.
These diseases are caused by variants in single genes that tend to have a big impact on health, making the genetic contributions to the illnesses relatively easy to find using current methods that rely on gathering family information, or pedigrees.
Genetic variation has been shown to affect the response of patients to drugs, toxic substances and other environmental factors.
www.genome.gov /10005336   (1993 words)

  
 Mycology Workshop, August 2000   (Site not responding. Last check: 2007-10-16)
With Cryptococcus neoformans, genetic isolation among serotypes A, D and B+C has been shown to be as great as between species of other fungi, and there is evidence of hybridization between individuals of serotypes A and D. The third important area is the relationship between environmental and clinical isolates of human pathogenic fungi.
The fourth important area is the use of genetic variation in host genotype to prevent disease by identifying susceptible host populations.
Variation in host genotype is supporting genome wide profiling which is leading to identifying host groups at risk for disease, monitoring markers that are surrogates for host response to disease and treatment, and using peripheral blood cells to interrogate the condition of deeper host tissues and organs.
www.niaid.nih.gov /dmid/meetings/mycology2000/genetic.htm   (898 words)

  
 Genetic variation map may promise tailored drugs - genetics - 18 February 2005 - New Scientist   (Site not responding. Last check: 2007-10-16)
A study of 1.58 million genetic markers across 71 individuals of different genetic heritage showed that the markers correspond to general genetic variation.
These patterns of genetic variation could be used to identify genetic susceptibility to certain illnesses and anticipate the varying responses to treatments in different people.
This variability can play an important role in determining a person's susceptibility to certain illnesses, such as cardiovascular disease and mental illness - conditions usually caused by a multiplicity of genetic and environmental factors.
www.newscientist.com /channel/life/genetics/dn7027-genetic-variation-map-may-promise-tailored-drugs.html   (483 words)

  
 Genetic Variation in the Siskiyou Mountains Salamander
The purpose of this research is to determine the genetic diversity in the Siskiyou Mountains salamander in order to estimate 1) the potential for independently evolving lineages, and 2) effective population sizes and migration rate of individuals among populations.
The number of independently evolving lineages and potential for gene flow among populations is estimated by analyzing the genetic variation within a single gene that codes for ATPase 6 in mitochondrial DNA (mtDNA).
In contrast, if genetic diversity is low, indicating that some level of migration or gene flow among populations is occurring, connectivity between populations by providing dispersal corridors for that migration may be needed.
www.reo.gov /ama/applegate_info/genetic_variation.htm   (730 words)

  
 Genetic variation, classification and 'race' - Nature Genetics
We review the results of genetic analyses that show that human genetic variation is geographically structured, in accord with historical patterns of gene flow and genetic drift.
Genetic variation is geographically structured, as expected from the partial isolation of human populations during much of their history.
Fortunately, modern human genetics can deliver the salutary message that human populations share most of their genetic variation and that there is no scientific support for the concept that human populations are discrete, nonoverlapping entities.
www.nature.com /cgi-taf/DynaPage.taf?file=/ng/journal/v36/n11s/full/ng1435.html   (4390 words)

  
 Genetic Variation and Heart Failure
The genetic variance occurs in the beta-1 adrenergic receptor, which is the target for beta-blockers.
This is especially the case with beta-blockers, one of the cornerstones in the treatment of heart failure,” says Michael Bristow, M.D., Ph.D., a cardiologist at the University of Colorado School of Medicine and one of the study’s authors.
The researchers also looked at the genetic variants and the response to the beta blocker in fl patients compared to whites, and found that genetics and not race determined who benefited best from the drug.
www.umm.edu /news/releases/genetic_variation.htm   (1051 words)

  
 International Consortium Completes Map of Human Genetic Variation, October 26, 2005 Press Release - National Institutes ...
Genetic diversity in humans is increased by recombination, which is the swapping of DNA from the maternal and paternal lines.
As expected, the vast majority of both rare and common patterns of genetic variation were found in all of the populations studied.
However, the consortium did find evidence that a very small subset of human genetic variation may be related to selection pressures related to geographic or environmental factors, such as microorganisms that cause infectious diseases.
www.nih.gov /news/pr/oct2005/nhgri-26.htm   (1829 words)

  
 Genetic Variation for Phenotypically Invariant Traits Detected in Teosinte: Implications for the Evolution of Novel ...
cryptic genetic variation in teosinte for traits that are invariant
varied considerably for the traits that distinguish maize and
for >14% of the phenotypic variance in the testcross population
www.genetics.org /cgi/content/full/160/1/333   (5052 words)

  
 The Mouse Genetic Variation Mapping (VMap) Initiative: Mapping SNPs, INDELs and Haplotype Blocks in the Mouse Genome - ...
Genetic variants are important tools in medical research, DNA forensics, and in the study of evolutionary biology.
To understand the health significance of genetic variation, the biological impact of any given variant (or haplotype block) in combination with environmental exposures should be assessed in a coordinated fashion.
Because a dense variant map of the mouse will be an important tool for studies of gene-environment and gene-gene interactions and would greatly enhance progress in understanding the corresponding interactions in humans.
www.niehs.nih.gov /oc/factsheets/mouse.htm   (683 words)

  
 Sexual Sources Of Genetic Variation   (Site not responding. Last check: 2007-10-16)
Meiosis and fertilization are the primary source of genetic variation in sexually reproducing organisms due to the sorting and recombining of genetic information that occurs in these processes.
The significance of this variability is that the maternal and paternal homologues will carry different genetic information at many of their corresponding loci.
The three sources of genetic variability in sexually reproducing organisms (independent assortment, crossing over, and random fertilization) produce various genetic combinations carried by individuals of a population and affect how successfully an individual will cope with its environment.
www.radford.edu /~rsheehy/genetics/Meiosis/B245OMeiVar.html   (572 words)

  
 Genetic variation
The abundant gene variability presents major challenges to the analysis and establishment of complex genotype/haplotype phenotype relationships against a background of high natural genome sequence diversity.
At present, substantial data sets from the comparative candidate gene sequence analysis in an average of several hundred individuals are being tested and analysed in collaboration with international institutions with respect to given genetic variation, underlying haplotype structures and the extraction of phenotypically relevant patterns of variants.
Importantly, the collaborators constituting this network have already shown to be capable of generating positive results in terms of potential genetic risk factors, drug target candidates and genetic variants of predictive value.
www.molgen.mpg.de /~genetic-variation/Projects.html   (1367 words)

  
 SNPs & other genetic variations and pharmaceuticals glossary
Genetic changes that have been associated with disease risk or were caused by damage inflicted by external agents (such as radiation) are particularly described as mutations.
Genetic variations, broadly encompassing any of the many types of variations in DNA sequence that are found within a given population.
The study of the genetic composition of populations and of the effects of factors such as selection, population size, mutation, migration, and genetic drift on the frequencies of various genotypes and phenotypes.
www.genomicglossaries.com /content/genetic_variations_gloss.asp   (6643 words)

  
 The Measurement of Genetic Variation
Although electrophoretically-evident variation is only a small portion of the genetic variation of a gene, many enzymes have been shown to exhibit high levels of allozymic variation.
The next step in the measurement of genetic diversity is to calculate one of numerous statistics that take into account the numbers and/or types of variants of a genetic trait.
There are two fundamental types of genetic diversity statistics: one is based on the numbers of differences between variants and one is based on the number of variants.
www.agu.org /revgeophys/buckli01/node3.html   (622 words)

  
 Evolution - A-Z - Genetic variation
The extent of variation in natural populations is such that every individual must be genetically unique.
Important though this is, if there were no pre-existing allelic variation, recombination and migration would not generate new genetic variants.
Even in a population in which all copies of a chromosome were identical, new genetic variants would arise by mutation.
www.blackwellpublishing.com /ridley/a-z/Genetic_variation.asp   (197 words)

  
 Genetic variation, nutrition, and chronic diseases - Genetic Variation and Nutrition, part 2 Nutrition Today - Find ...
Obesity is a heterogeneous disorder, the result of genetic and environmental factors.[13] Twin studies indicate that obesity is familial with strong genetic components, although specific gene(s), genetic markers, or genetically determined mechanisms have not been identified yet.
One of the most revealing experiences about the effects of the genes on human body fat variation occurs when humans are exposed to either a standardized chronic overfeeding treatment or a negative balance regimen.
In the overfeeding twin study by Bouchard et al.,[162] the variation within pairs was one third of the variation between pairs.
www.findarticles.com /p/articles/mi_m0841/is_n5_v30/ai_17798844/pg_4   (516 words)

  
 Amazon.ca: Adaptive Genetic Variation in the Wild: Books: Timothy A. Mousseau   (Site not responding. Last check: 2007-10-16)
"Adaptive Genetic Variation in the Wild proposes the idea that a fundamental objective of evolutionary ecology is to predict individual, population, community, and ecosystem response to environmental.
A number of these questions are longstanding, such as how within-population genetic variation is transplanted into variation among populations and variation among species, what mechanisms maintain genetic variation in the face of selection, and to what extent changing environments and genotype X environment interactions influence and maintain variation.
"Adaptive Genetic Variation in the Wild proposes the idea that a fundamental objective of evolutionary ecology is to predict individual, population, community, and ecosystem response to environmental chance.
www.amazon.ca /Adaptive-Genetic-Variation-Timothy-Mousseau/dp/019512183X   (944 words)

  
 Genetic Variation in the Australian Dingo
Hybridisation may cause genetic change in the population and, although there is strong strong social pressure to avoid it because of the damage it may cause, there are no long term studies on whether it would actually have an adverse effect.
It is often difficult to find variation in a functional gene within a species but crosses between related species that produce fertile offspring are often extremely useful because accumulation of genetic differences often produces fixed differences at large numbers of loci.
Type a number of dingoes and dogs for highly variable markers to develop several markers which are diagnostic for dog genetic material and for dingo genetic material.
www.wolfweb.com.au /acd/genvarindingo.htm   (3267 words)

  
 Human genetic variation - Wikipedia, the free encyclopedia
Studies of human genetic variation imply that Africa was the ancestral source of all modern humans, and that Homo sapiens migrated out of Africa and displaced Homo erectus between 140,000 and 290,000 years ago (Cann et al.
The genetic variation seen outside Africa is generally a subset of the variation within Africa, a pattern that would be produced if the migrants from Africa were limited in number and carried just part of African genetic variability with them (Cavalli-Sforza and Feldman 2003).
In the field of population genetics, it is believed that the distribution of neutral polymorphisms among contemporary humans reflects human demographic history.
en.wikipedia.org /wiki/Human_genetic_variation   (3744 words)

  
 Variation and Mendel's Laws
In the case of meiotic replication, the shared genetic information conveyed and expressed by an organism is governed by certain genetic principles.
Mendel's first principle of genetics, states that the sex cell of a plant or animal may contain one factor (allele) for different traits but not both factors needed to express the traits.
These genetic principles have become characteristically known as the law of independent assortment (Mendel's second principle), and Dominants and Recessives (Mendel's third principle).
www.mnsu.edu /emuseum/biology/evolution/genetics/mendelsvariation.html   (571 words)

  
 Other Sources of Genetic Variation
Mendelian Genetics can only account for a majority of the genetic variations in species seen on earth.
In genetic drift, random variation occurs because the genetic population is small, leading to the proliferation of specific traits within a population.
The high occurrence of deafness was a result of genetic drift, in that the population was so small that differing traits from outside populations could not enter in.
www.mnsu.edu /emuseum/biology/evolution/genetics/sourcesofgeneticvariation.html   (377 words)

  
 NIH Curriculum Supplement Series for High School - Human Genetic Variation
Study the basics of human genetics; its potential to improve human health; and its application towards understanding and describing human evolution.
CD-ROM-based activity illustrates DNA sequences are responsible for genetic differences, and associated with disease, survival, evolution.
A family's case study on genetic variation testing exemplifies difficult moral and social questions for our society.
science-education.nih.gov /Customers.nsf/HSGenetic?OpenForm&CS_11=false&CS_12=false&CS_13=false&CS_22=false&   (200 words)

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