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  • clone | genetics | Britannica.com
    bacteria and yeasts are clones of parent cells generated by either binary fission or budding The body cells of plants and animals are clones ultimately derived from the mitosis cell reproduction of a single fertilized egg More narrowly a clone can be defined as an individual organism that was grown from a single body cell of its parent and that is 100 of 185 words Images About Us About Our

    Original URL path: http://www.britannica.com/science/clone-genetics (2016-02-13)
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  • Human Genome Project | scientific project | Britannica.com
    000 genes Advances based on the Human Genome Project Advances in genetics and genomics continue to emerge Two important advances include the International HapMap Project and the initiation of large scale comparative genomics studies both of which have been made possible by the availability of databases of genomic sequences of humans as well as the availability of databases of genomic sequences of a multitude of other species The International HapMap Project is a collaborative effort between Japan the United Kingdom Canada China Nigeria and the United States in which the goal is to identify and catalog genetic similarities and differences between individuals representing four major human populations derived from the continents of Africa Europe and Asia The identification of genetic variations called polymorphisms that exist in DNA sequences among populations allows researchers to define haplotypes markers that distinguish specific regions of DNA in the human genome Association studies of the prevalence of these haplotypes in control and patient populations can be used to help identify potentially functional genetic differences that predispose an individual toward disease or alternatively that may protect an individual from disease Similarly linkage studies of the inheritance of these haplotypes in families affected by a known genetic trait can also help to pinpoint the specific gene or genes that underlie or modify that trait Association and linkage studies have enabled the identification of numerous disease genes and their modifiers In contrast to the International HapMap Project which compares genomic sequences within one species comparative genomics is the study of similarities and differences between different species In recent years a staggering number of full or almost full genome sequences from different species have been determined and deposited in public databases such as NIH s Entrez Genome database By comparing these sequences often using a software tool called BLAST Basic Local Alignment Search Tool researchers are able to identify degrees of similarity and divergence between the genes and genomes of related or disparate species The results of these studies have illuminated the evolution of species and of genomes Such studies have also helped to draw attention to highly conserved regions of noncoding sequences of DNA that were originally thought to be nonfunctional because they do not contain base sequences that are translated into protein However some noncoding regions of DNA have been highly conserved and may play key roles in human evolution Impacts of the Human Genome Project Impact on medicine Human Genome Project Punctum Press and Information Office of the Federal Government of Germany The public availability of a complete human genome sequence represented a defining moment for both the biomedical community and for society In the years since completion of the Human Genome Project the human genome database together with other publicly available resources such as the HapMap database has enabled the identification of a variety of genes that are associated with disease This in turn has enabled more objective and accurate diagnoses in some cases even before the onset of overt clinical symptoms Association and linkage

    Original URL path: http://www.britannica.com/event/Human-Genome-Project (2016-02-13)
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  • epigenetics | Britannica.com
    reproduce whether by meiosis or mitosis thereby precluding their inheritance Impact of epigenetics on biomedicine Epigenetic changes not only influence the expression of genes in plants and animals but also enable the differentiation of pluripotent stem cells cells having the potential to become any of many different kinds of cells In other words epigenetic changes allow cells that all share the same DNA and are ultimately derived from one fertilized egg to become specialized for example as liver cells brain cells or skin cells As the mechanisms of epigenetics have become better understood researchers have recognized that the epigenome chemical modification at the level of the genome also influences a wide range of biomedical conditions This new perception has opened the door to a deeper understanding of normal and abnormal biological processes and has offered the possibility of novel interventions that might prevent or ameliorate certain diseases Epigenetic contributions to disease fall into two classes One class involves genes that are themselves regulated epigenetically such as the imprinted parent specific genes associated with Angelman syndrome or Prader Willi syndrome Clinical outcomes in cases of these syndromes depend on the degree to which an inherited normal or mutated gene is or is not expressed The other class involves genes whose products participate in the epigenetic machinery and thereby regulate the expression of other genes For example the gene MECP2 methyl CpG binding protein 2 encodes a protein that binds to specific methylated regions of DNA and contributes to the silencing of those sequences Mutations that impair the MECP2 gene can lead to Rett syndrome Many tumours and cancers are believed to involve epigenetic changes attributable to environmental factors These changes include a general decrease in methylation which is thought to contribute to the increased expression of growth promoting genes punctuated by gene specific increases in methylation that are thought to silence tumour suppressor genes Epigenetic signaling attributed to environmental factors has also been associated with some characteristics of aging by researchers that studied the apparently unequal aging rates in genetically identical twins One of the most promising areas of epigenetic investigation involves stem cells Researchers have understood for some time that epigenetic mechanisms play a key role in defining the potentiality of stem cells As those mechanisms become clearer it may become possible to intervene and effectively alter the developmental state and even the tissue type of given cells The implications of this work for future clinical regenerative intervention for conditions ranging from trauma to neurodegenerative disease are profound Judith L Fridovich Keil Comments Share Email Print Cite You may also be interested in eugenics genetics genomics cytogenetics biology science life behaviour genetics polymerase chain reaction microbiology DNA fingerprinting human genetics Keep exploring Biology Bonanza Chemistry and Biology Fact or Fiction Nature Tip of the Iceberg Quiz 5 Surprising Facts About Bats 10 Important Dates in Mars History What made you want to look up epigenetics To From Subject Comments Please limit to 900 characters Cancel Britannica Stories Behind The News

    Original URL path: http://www.britannica.com/science/epigenetics (2016-02-13)
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  • genomics | Britannica.com
    cannot be deduced these functions gradually become revealed with further research Genomics applications Functional genomics Australian sheep blow fly genome University of Melbourne Victoria Australia A Britannica Publishing Partner Analysis of genes at the functional level is one of the main uses of genomics an area known generally as functional genomics Determining the function of individual genes can be done in several ways Classical or forward genetic methodology starts with a randomly obtained mutant of interesting phenotype and uses this to find the normal gene sequence and its function Reverse genetics starts with the normal gene sequence as obtained by genomics induces a targeted mutation into the gene then by observing how the mutation changes phenotype deduces the normal function of the gene The two approaches forward and reverse are complementary Often a gene identified by forward genetics has been mapped to one specific chromosomal region and the full genomic sequence reveals a gene in this position with an already annotated function For more information about genetic studies see genetics Methods in genetics Gene identification by microarray genomic analysis Genomics has greatly simplified the process of finding the complete subset of genes that is relevant to some specific temporal or developmental event of an organism For example microarray technology allows a sample of the DNA of a clone of each gene in a whole genome to be laid out in order on the surface of a special chip which is basically a small thin piece of glass that is treated in such a way that DNA molecules firmly stick to the surface For any specific developmental stage of interest e g the growth of root hairs in a plant or the production of a limb bud in an animal the total RNA is extracted from cells of the organism labeled with a fluorescent dye and used to bathe the surfaces of the microarrays As a result of specific base pairing the RNAs present bind to the genes from which they were originally transcribed and produce fluorescent spots on the chip s surface Hence the total set of genes that were transcribed during the biological function of interest can be determined Note that forward genetics can aim at a similar goal of assembling the subset of genes that pertain to some specific biological process The forward genetic approach is to first induce a large set of mutations with phenotypes that appear to change the process in question followed by attempts to define the genes that normally guide the process However the technique can only identify genes for which mutations produce an easily recognizable mutant phenotype and so genes with subtle effects are often missed Comparative genomics A further application of genomics is in the study of evolutionary relationships Using classical genetics evolutionary relationships can be studied by comparing the chromosome size number and banding patterns between populations species and genera However if full genomic sequences are available comparative genomics brings to bear a resolving power that is much greater than that

    Original URL path: http://www.britannica.com/science/genomics (2016-02-13)
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  • cytogenetics | biology | Britannica.com
    are first treated with heat resulting in patterns that are easier to analyze In C banding regions of chromosomes containing heterochromatin the condensed inactive form of DNA are stained FISH is used to examine specific DNA sequences and the number or structure of chromosomes The technique is based on the use of fluorescent probes that are capable of detecting particular DNA sequences FISH is a rapid and highly sensitive technique and often is used to detect genetic abnormalities in embryos preimplantation genetic diagnosis Rahul Gladwin Comments Share Email Print Cite You may also be interested in genetics biology science eugenics epigenetics genomics life behaviour genetics microbiology classification polymerase chain reaction ecology Keep exploring Biology Bonanza Chemistry and Biology Fact or Fiction Nature Tip of the Iceberg Quiz 8 Animals That Suck Blood Off the Hook 10 Sharks Protected From Fishing in American Waters What made you want to look up cytogenetics To From Subject Comments Please limit to 900 characters Cancel Britannica Stories Behind The News Philosophy Religion Healing the Schism Pope Meets Patriarch Behind The News Science Gravitational Waves Observed Spotlight History Thomas Malthus s 250th Birthday See More Stories FEATURED QUIZZES Vocabulary Quiz True or False Spell It See More Quizzes About Us About Our Ads Contact Us Privacy Policy Terms of Use 2016 Encyclopædia Britannica Inc MLA style cytogenetics Encyclopædia Britannica Encyclopædia Britannica Online Encyclopædia Britannica Inc 2016 Web 12 Feb 2016 http www britannica com science cytogenetics APA style cytogenetics 2016 In Encyclopædia Britannica Retrieved from http www britannica com science cytogenetics Harvard style cytogenetics 2016 Encyclopædia Britannica Online Retrieved 12 February 2016 from http www britannica com science cytogenetics Chicago Manual of Style Encyclopædia Britannica Online s v cytogenetics accessed February 12 2016 http www britannica com science cytogenetics While every effort has been made

    Original URL path: http://www.britannica.com/science/cytogenetics (2016-02-13)
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  • behaviour genetics | Britannica.com
    such as behaviour The twin method relies on the accident of nature that results in identical monozygotic MZ twins or fraternal dizygotic DZ twins MZ twins are like clones genetically identical to each other because they came from the same fertilized egg DZ twins on the other hand developed from two eggs that happened to be fertilized at the same time Like other siblings DZ twins are only half as similar genetically as MZ twins To the extent that behavioral variability is caused by environmental factors DZ twins should be as similar for the behavioral trait as are MZ twins because both types of twins are reared by the same parents in the same place at the same time If the trait is influenced by genes then DZ twins ought to be less similar than MZ twins For schizophrenia for example the concordance risk of one twin s being schizophrenic if the other is is about 45 percent for MZ twins and about 15 percent for DZ twins For intelligence as assessed by IQ tests the correlation an index of resemblance 0 00 indicates no resemblance and 1 00 indicates perfect resemblance is 0 85 for MZ twins and 0 60 for DZ twins for studies throughout the world of more than 10 000 pairs of twins The twin method has been robustly defended as a rough screen for genetic influence on behaviour The adoption method is a quasi experimental design that relies on a social accident in which children are adopted away from their biological birth parents early in life thus cleaving the effects of nature and nurture Because the twin and adoption methods are so different greater confidence is warranted when results from these two methods converge on the same conclusion as they usually do An influential adoption study of schizophrenia in 1966 by American behavioral geneticist Leonard Heston showed that children adopted away from their schizophrenic biological mothers at birth were just as likely to become schizophrenic about 10 percent as were children reared by their schizophrenic biological mothers A 20 year study begun in the 1970s in the United States of intelligence of adopted children and their biological and adoptive parents showed increasing similarity from infancy to childhood to adolescence between the adopted children and their biological parents but no resemblance between the adopted children and their adoptive parents In contrast to traditional molecular genetic research that focused on rare disorders caused by a single genetic mutation molecular genetic research on complex behavioral traits and common behavioral disorders is much more difficult because multiple genes are involved and each gene has a relatively small effect However some genes identified in animal models have contributed to an improved understanding of complex human behavioral disorders such as reading disability hyperactivity autism and dementia Robert Plomin Comments Share Email Print Cite Last Updated 1 22 2016 You may also be interested in science life psychology behavioral science psychopharmacology culture and personality studies biology cognitive science forensic psychology neuropsychology biological

    Original URL path: http://www.britannica.com/science/behaviour-genetics (2016-02-13)
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  • polymerase chain reaction | biochemistry | Britannica.com
    is carried out in repeated cycles The initial step is the denaturation or separation of the two strands of the DNA molecule This is accomplished by heating the starting material to temperatures of about 95 C 203 F Each strand is a template on which a new strand is built In the second step the temperature is reduced to about 55 C 131 F so that the primers can anneal to the template In the third step the temperature is raised to about 72 C 162 F and the DNA polymerase begins adding nucleotides onto the ends of the annealed primers At the end of the cycle which lasts about five minutes the temperature is raised and the process begins again The number of copies doubles after each cycle Usually 25 to 30 cycles produce a sufficient amount of DNA In the original PCR procedure one problem was that the DNA polymerase had to be replenished after every cycle because it is not stable at the high temperatures needed for denaturation This problem was solved in 1987 with the discovery of a heat stable DNA polymerase called Taq an enzyme isolated from the thermophilic bacterium Thermus aquaticus which inhabits hot springs Taq polymerase also led to the invention of the PCR machine Because DNA from a wide range of sources can be amplified the technique has been applied to many fields PCR is used to diagnose genetic disease and to detect low levels of viral infection In forensic medicine it is used to analyze minute traces of blood and other tissues in order to identify the donor by his genetic fingerprint The technique has also been used to amplify DNA fragments found in preserved tissues such as those of a 40 000 year old frozen woolly mammoth or of a 7 500 year old human found in a peat bog Comments Share Email Print Cite Last Updated 3 21 2014 You may also be interested in DNA fingerprinting complementation test genetics toxicological examination science anatomy toxicology test eugenics ecology chemotherapy quinine epigenetics Keep exploring Biology Bonanza Chemistry and Biology Fact or Fiction Human Health Fact or Fiction 8 Animals That Suck Blood 10 Places to Visit in the Solar System What made you want to look up polymerase chain reaction To From Subject Comments Please limit to 900 characters Cancel Britannica Stories Behind The News Philosophy Religion Healing the Schism Pope Meets Patriarch Behind The News Science Gravitational Waves Observed Spotlight History Thomas Malthus s 250th Birthday See More Stories FEATURED QUIZZES Vocabulary Quiz True or False Spell It See More Quizzes About Us About Our Ads Contact Us Privacy Policy Terms of Use 2016 Encyclopædia Britannica Inc MLA style polymerase chain reaction Encyclopædia Britannica Encyclopædia Britannica Online Encyclopædia Britannica Inc 2016 Web 12 Feb 2016 http www britannica com science polymerase chain reaction APA style polymerase chain reaction 2016 In Encyclopædia Britannica Retrieved from http www britannica com science polymerase chain reaction Harvard style polymerase chain reaction 2016 Encyclopædia

    Original URL path: http://www.britannica.com/science/polymerase-chain-reaction (2016-02-13)
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  • microbiology | Britannica.com
    group of minute simple life forms that include bacteria archaea algae fungi protozoa and viruses The field is concerned with the structure function and classification of such organisms and with ways of both exploiting and controlling their activities The 17th century discovery of living forms existing invisible to the naked eye was a significant milestone in the history of science for from the 13th century onward it had been postulated

    Original URL path: http://www.britannica.com/science/microbiology (2016-02-13)
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