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, the molecular basis for inheritance. Each strand of DNA is a chain of
nucleotides, matching each other in the center to form what look like rungs on a twisted ladder.
Genetics is the
science of heredity and Genetic variation in living organisms. ISBN 0-7167-3520-2. 854 pages. ISBN 0-7637-1511-5. Knowledge of the inheritance of characteristics has been implicitly used since
prehistoric times for improving crop plants and animals through
selective breeding. However, the modern science of genetics, which seeks to understand the mechanisms of inheritance, only began with the work of
Gregor Mendel in the mid-1800s. Although he did not know the physical basis for heredity, Mendel observed that inheritance is fundamentally a
discrete process with specific traits that are inherited in an independent manner — these basic units of inheritance are now called genes.
Following the rediscovery of Gregor Johann Mendel's observations in the early
1900s, research in 1910s yielded the first physical understanding of inheritance — that genes are arranged linearly along large
cell (biology) structures called
chromosomes. By the
1950s it was understood that the core of a chromosome was a long molecule called DNA and genes existed as linear sections within the molecule. A single strand of DNA is a chain of four types of
nucleotides; hereditary information is contained within the sequence of these nucleotides. Solved by James Watson,
Maurice_Wilkins, and Francis Crick in 1953, DNA's three-dimensional structure is a double helix, with the nucleotides on each strand physically Base pairing to each other. Each strand acts as a template for synthesis of a new partner strand, providing the physical mechanism for the inheritance of information.
The sequence of nucleotides in DNA is used to produce specific sequences of amino acids, creating
proteins — a correspondence known as the "genetic code". This sequence of amino acids in a protein determines how it folds into a three-dimensional structure, this structure is in turn responsible for the protein's function. Proteins are responsible for almost all functional roles in the cell. A change to DNA sequence can change a protein's structure and behavior, and this can have dramatic consequences in the cell and on the organism as a whole.
Although genetics plays a large role in determining the appearance and behavior of organisms, it is the interaction of genetics with the environment an organism experiences that determines the ultimate outcome. For example, while genes play a role in determining a person's
human height, the
nutrition and health that person experiences in childhood also have a large effect.
History of genetics
led him to the hypothesis that genes are located upon chromosomes.
Although the science of genetics has its origins in the work of Gregor Mendel in the mid-1800s, various theories of inheritance preceded Mendel. These theories generally assumed that there existed an
inheritance of acquired characteristics (also known as "soft inheritance"): the belief that individuals inherit traits that have been strengthened in their parents. Today, the theory is commonly associated with Jean-Baptiste Lamarck, who used this pattern of inheritance to explain the evolution of various traits within species (these changes are now understood to be the product of natural selection rather than a product of
soft inheritance).
Mendelian and classical genetics
The modern science of genetics traces its roots to the observations made by
Gregor Johann Mendel, a German-Czech Augustinian monk and scientist who made detailed studies of the nature of inheritance in plants. In his paper "Versuche über Pflanzenhybriden" ("
Experiments on 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. (in English in 1901, J. R. Hortic. Soc. 26: 1–32) Online copy of William Bateson's letter to Adam Sedgwick. The adjective "genetic" (derived from the Greek language word "genno"
γεννώ: to give birth) predates the noun, dating back to the 1830's and first used in the biological sense in
1859 by Charles Darwin in the The Origin of Species.genetic,
a. and
n. pl., Oxford English Dictionary, 2nd ed. (1989) Bateson publicly promoted and popularized usage of word "genetics" to describe the study of inheritance in his inaugural address to the Third International Conference on Plant Hybridization in London, England, in 1906.
Although the conference was titled "International Conference on Hybridisation and Plant Breeding", Wilks changed the title for publication as a result of Bateson's speech.
In the decades following rediscovery and popularization of Mendel's work, numerous experiments sought to elucidate the molecular basis of DNA. In 1910 Thomas Hunt Morgan argued that genes reside on chromosomes, based on observations of a sex-linked white eye mutation in fruit flies. In 1913 his student
Alfred Sturtevant used the phenomenon of
genetic linkage and the associated recombination rates to demonstrate and map the linear arrangement of genes upon the chromosome.
Molecular genetics
Although chromosomes were known to contain genes, chromosomes were composed of both protein and DNA — it was unknown which was critical for heredity or how the process occurred. In 1928,
Frederick Griffith published his discovery of the phenomenon of
Transformation (genetics) (see Griffith's experiment); sixteen years later, in 1944, Oswald Theodore Avery,
Colin McLeod and Maclyn McCarty used this phenomenon to isolate and identify the molecule responsible for transformation as DNA. 35th anniversary reprint available The Hershey-Chase experiment in 1952 identified DNA (rather than protein) as the genetic material of viruses, further evidence that DNA was the molecule responsible for inheritance.
James D. Watson and Francis Crick resolved the structure of DNA in 1953, using the X-ray crystallography work of
Rosalind Franklin that indicated the molecule had a helical structure. Their double-helix model paired a sequence of nucleotides with a "complement" on the other strand. This structure not only provided a physical explanation for information contained within the order of the nucleotides, but also a physical mechanism for duplication through separation of strands and the reconstruction of a partner strand based on the nucleotide pairings. Although the structure explained the process of inheritance, it was still unknown how DNA influenced the behavior of cells. In the following years many scientists sought to understand how DNA controls the process of
protein production within ribosomes, eventually discovering the transcription of DNA into
messenger RNA and uncovering the genetic code which links the nucleotide sequence of
messenger RNA to the amino acid sequence of protein.
With this molecular understanding of DNA, an explosion of research based on this understanding of the molecular nature of DNA became possible. The development of chain-termination
DNA sequencing in 1977 enabled the determination of nucleotide sequences on DNA,
Genetics Online
Publishes the results of original research in genetics, biochemistry and molecular biology. Includes article abstracts. Full text requires subscription.
Genetics -- Archive of Issues by Date
Full Text and Abstracts January 1998– August 2008:
Genetics Society - Home
Organises a wide-ranging programme of scientific meetings covering all areas of genetics and co-owns and manages some of the leading academic journals in the field. Also represents ...
Genetics Society - Home
The Genetics Society was founded by William Bateson in 1919 and is one of the oldest “learned societies” devoted to Genetics in the world. Its membership of over 2000 consists ...
University of Cambridge, Department of Genetics
Includes details of research groups, information for current and prospective students, and a brief history of the department.
Medical Glossary - NHS Direct
Chorionic villus sampling is a test during pregnancy to see if there are any genetic problems with the foetus. A small sample of tissue is taken from the placenta.
Crucial Genetics // For expert advice on Paternity Testing, call us on ...
Crucial Genetics your solution to paternity testing, ISO Accredited, Specialists in Paternity Testing utilising in-home buccal swabs. Crucial Genetics offers accurate, affordable ...
Genetic Food Alert
Genetic Food Alert is an initiative founded by members of the Wholefood Trade, campaigning against the use of Genetically Modified Foods. We are lobbying for a five year ... ...
Genetic Health - DNA and Genetic Testing Kits
Genetic health and genetic testing DNA profile looks at health through selected screening of genes and DNA shown by medical research to have an effect on your health and ageing ...
Genetic Disorders Genetic Diseases Information Support & Help: GIG ...
UK-based organisation that aims to increase the public/government profile of genetic conditions. The AIS Support Group (UK) is affiliated to GIG.