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Genetics

2007 Schools Wikipedia Selection. Related subjects: General Biology

   Genetics (from the Greek genno γεννώ= give birth) is the science of
   genes, heredity, and the variation of organisms. The word "genetics"
   was first suggested to describe the study of inheritance and the
   science of variation by the prominent British scientist William Bateson
   in a personal letter to Adam Sedgwick, dated April 18, 1905. Bateson
   first used the term "genetics" publicly at the Third International
   Conference on Genetics (London, England) in 1906.

   Heredity and variations form the basis of genetics. Humans applied
   knowledge of genetics in prehistory with the domestication and breeding
   of plants and animals. In modern research, genetics provides important
   tools for the investigation of the function of a particular gene, e.g.,
   analysis of genetic interactions. Within organisms, genetic information
   generally is carried in chromosomes, where it is represented in the
   chemical structure of particular DNA (deoxyribonucleic acid) molecules.

   Genes encode the information necessary for synthesizing the amino-acid
   sequences in proteins, which in turn play a large role in determining
   the final phenotype, or physical appearance, of the organism. In
   diploid organisms, a dominant allele on one chromosome will mask the
   expression of a recessive gene on the other.

   The phrase to code for is often used to mean a gene contains the
   instructions about how to build a particular protein, as in the gene
   codes for the protein. The "one gene, one protein" concept is now known
   to be simplistic. For example, a single gene may produce multiple
   products, depending on how its transcription is regulated. Genes code
   for the nucleotide sequences in mRNA, tRNA and rRNA, required for
   protein synthesis.

   Genetics determines much (but not all) of the appearance of organisms,
   including humans, and possibly how they act. Environmental differences
   and random factors also play a part. Monozygotic ("identical") twins, a
   clone resulting from the early splitting of an embryo, have the same
   DNA, but different personalities and fingerprints.
   Genetically-identical plants grown in colder climates incorporate
   shorter and less-saturated fatty acids to avoid stiffness.

History

   In his paper "Versuche über Pflanzenhybriden" ("Experiments in Plant
   Hybridization"), presented in 1865 to the Brunn Natural History
   Society, Gregor Mendel traced the inheritance patterns of certain
   traits in pea plants and showed that they could be described
   mathematically. Although not all features show these patterns of
   Mendelian inheritance, his work suggested the utility of the
   application of statistics to the study of inheritance. Since that time
   many more complex forms of inheritance have been demonstrated.

   The significance of Mendel's work was not understood until early in the
   twentieth century, after his death, when his research was re-discovered
   by other scientists working on similar problems.

   Mendel did not understand the nature of inheritance. We now know that
   some heritable information is carried in DNA. ( Retroviruses, including
   influenza, oncoviruses and HIV, and many plant viruses, carry
   information as RNA.) Manipulation of DNA can in turn alter the
   inheritance and features of various organisms.

Timeline of notable discoveries

          1859 Charles Darwin publishes The Origin of Species
          1865 Gregor Mendel's paper, Experiments on Plant Hybridization
          1869 Friedrich Miescher discovers a weak acid in the nuclei of
          white blood cells that today we call DNA (Hartl and Jones).
          1903 Chromosomes are discovered to be hereditary units
          1906 The term "genetics" is first introduced publicly by the
          British biologist William Bateson at the Third International
          Conference on Genetics in London, England.
          1910 Thomas Hunt Morgan shows that genes reside on chromosomes,
          and discovered linked genes on chromosomes that do not follow
          Mendel's law of independent allele segregation
          1913 Alfred Sturtevant makes the first genetic map of a
          chromosome
          1913 Gene maps show chromosomes containing linear arranged genes
          1918 Ronald Fisher publishes On the correlation between
          relatives on the supposition of Mendelian inheritance - the
          modern synthesis starts.
          1927 Physical changes in genes are called mutations
          1928 Frederick Griffith discovers a hereditary molecule that is
          transmissible between bacteria (see Griffiths experiment)
          1931 Crossing over is the cause of recombination (see Barbara
          McClintock and cytogenetics)
          1941 Edward Lawrie Tatum and George Wells Beadle show that genes
          code for proteins; see the original central dogma of genetics
          1944 Oswald Theodore Avery, Colin McLeod and Maclyn McCarty
          isolate DNA as the genetic material (at that time called
          transforming principle)
          1950 Erwin Chargaff shows that the four nucleotides are not
          present in nucleic acids in stable proportions, but that some
          general rules appear to hold (e.g., the nucleotide bases
          Adenine-Thymine and Cytosine-Guanine always remain in equal
          proportions). Barbara McClintock discovers transposons in maize
          1952 The Hershey-Chase experiment proves the genetic information
          of phages (and all other organisms) to be DNA
          1953 DNA structure is resolved to be a double helix by James D.
          Watson and Francis Crick, with the help of Rosalind Franklin
          1956 Jo Hin Tjio and Albert Levan established the correct
          chromosome number in humans to be 46
          1958 The Meselson-Stahl experiment demonstrates that DNA is
          semiconservatively replicated
          1961 The genetic code is arranged in triplets
          1964 Howard Temin showed using RNA viruses that Watson's central
          dogma is not always true
          1970 Restriction enzymes were discovered in studies of a
          bacterium, Haemophilus influenzae, enabling scientists to cut
          and paste DNA
          1977 DNA is sequenced for the first time by Fred Sanger, Walter
          Gilbert, and Allan Maxam working independently. Sanger's lab
          complete the entire genome of sequence of Bacteriophage Φ-X174;.
          1983 Kary Banks Mullis discovers the polymerase chain reaction
          enabling the easy amplification of DNA
          1985 Alec Jeffreys discovers genetic finger printing.
          1989 The first human gene is sequenced by Francis Collins and
          Lap-Chee Tsui. It encodes the CFTR protein. Defects in this gene
          cause cystic fibrosis
          1995 The genome of Haemophilus influenzae is the first genome of
          a free living organism to be sequenced.
          1996 Saccharomyces cerevisiae is the first eukaryote genome
          sequence to be released
          1998 The first genome sequence for a multicellular eukaryote, C.
          elegans is released.
          2001 First draft sequences of the human genome are released
          simultaneously by the Human Genome Project and Celera Genomics.
          2003 ( 14 April) Successful completion of Human Genome Project
          with 99% of the genome sequenced to a 99.99% accuracy
          2006 Marcus Pembrey and Olov Bygren publish Sex-specific,
          male-line transgenerational responses in humans, a proof of
          epigenetics.

   josh was here

Areas of genetics

Classical genetics

          Main articles: Classical genetics, Mendelian inheritance

   Classical genetics consists of the techniques and methodologies of
   genetics that predate the advent of molecular biology. After the
   discovery of the genetic code and such tools of cloning as restriction
   enzymes, the avenues of investigation open to geneticists were greatly
   broadened. Some classical genetic ideas have been supplanted with the
   mechanistic understanding brought by molecular discoveries, but many
   remain intact and in use, such as Mendel's laws. Patterns of
   inheritance still remain a useful tool for the study of genetic
   diseases.

Behavioural genetics

          Main article: Behavioural genetics

   Behavioral genetics studies the influence of varying genetics on animal
   behavior. Behavioral genetics studies the effects of human disorders as
   well as its causes. Behavioural genetics has yielded some very
   interesting questions about the evolution of various behaviors, and
   even some fundamental principles of evolution in general. For example,
   guppies and meerkats seem to be genetically driven to post a lookout to
   watch for predators. This lookout stands a significantly slimmer chance
   of survival than the others, so because of the mechanism of natural
   selection, it would seem that this trait would be lost after a few
   generations. However, the gene has remained, leading evolutionary
   philosopher/scientists such as Richard Dawkins and W. D. Hamilton to
   propose explanations, including the theories of kin selection and
   reciprocal altruism. The interactions and behaviors of gregarious
   creatures is partially genetic in cause and must therefore be
   approached by evolutionary theory.

Clinical genetics

   Physicians who are trained as Geneticists diagnose, treat, and counsel
   patients with genetic disorders or syndromes. These doctors are
   typically trained in a genetics residency and/or fellowship.

   Clinical genetics is also the study of genetic causes of clinical
   diseases.

Molecular genetics

   Molecular genetics builds upon the foundation of classical genetics but
   focuses on the structure and function of genes at a molecular level.
   Molecular genetics employs the methods of both classical genetics (such
   as hybridization) and molecular biology. It is so-called to
   differentiate it from other sub fields of genetics such as ecological
   genetics and population genetics. An important area within molecular
   genetics is the use of molecular information to determine the patterns
   of descent, and therefore the correct scientific classification of
   organisms: this is called molecular systematics. The study of inherited
   features not strictly associated with changes in the DNA sequence is
   called epigenetics.

   Some take the view that life can be defined, in molecular terms, as the
   set of strategies which RNA polynucleotides have used and continue to
   use to perpetuate themselves. This definition grows out of work on the
   origin of life, specifically the RNA world hypothesis.

Population, quantitative and ecological genetics

          Main articles: Population genetics, Quantitative genetics,
          Ecological genetics

   Population, quantitative and ecological genetics are all very closely
   related subfields and also build upon classical genetics (supplemented
   with modern molecular genetics). They are chiefly distinguished by a
   common theme of studying populations of organisms drawn from nature but
   differ somewhat in the choice of which aspect of the organism on which
   they focus. The foundational discipline is population genetics which
   studies the distribution of and change in allele frequencies of genes
   under the influence of the four evolutionary forces: natural selection,
   genetic drift, mutation and migration. It is the theory that attempts
   to explain such phenomena as adaptation and speciation.

   The related subfield of quantitative genetics, which builds on
   population genetics, aims to predict the response to selection given
   data on the phenotype and relationships of individuals. A more recent
   development of quantitative genetics is the analysis of quantitative
   trait loci. Traits that are under the influence of a large number of
   genes are known as quantitative traits, and their mapping to a location
   on the chromosome requires accurate phenotypic, pedigree and marker
   data from a large number of related individuals.

   Ecological genetics again builds upon the basic principles of
   population genetics but is more explicitly focused on ecological
   issues. While molecular genetics studies the structure and function of
   genes at a molecular level, ecological genetics focuses on wild
   populations of organisms, and attempts to collect data on the
   ecological aspects of individuals as well as molecular markers from
   those individuals.

   Population genetics is closely linked with the methods of genetic
   epidemiology. One method to study gene-disease associations is using
   the principle of Mendelian randomization.

Genomics

   A more recent development is the rise of genomics, which attempts the
   study of large-scale genetic patterns across the genome for (and in
   principle, all the DNA in) a given species. The field typically depends
   on the availability of whole genome sequences, computational tools and
   Sequence profiling tool using bioinformatics approaches for analysis of
   large sets of data.

Closely-related fields

   The science which grew out of the union of biochemistry and genetics is
   widely known as molecular biology. The term "genetics" is often widely
   conflated with the notion of genetic engineering, where the DNA of an
   organism is modified for some kind of practical end, but most research
   in genetics is aimed at understanding and explaining the effect of
   genes on phenotypes and in the role of genes in populations (see
   population genetics and ecological genetics), rather than genetic
   engineering.

Journals

     * Genetics
     * Journal of Genetics
     * Annals of Human Genetics
     * Heredity

   Retrieved from " http://en.wikipedia.org/wiki/Genetics"
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   with only minor checks and changes (see www.wikipedia.org for details
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