"Gene" Definitions

Gene :

The basic biological unit of heredity. A segment of deoxyribonucleic acid (DNA) needed to contribute to a function.
An official definition: According to the official Guidelines for Human Gene Nomenclature, a gene is defined as "a DNA segment that contributes to phenotype/function. In the absence of demonstrated function a gene may be characterized by sequence, transcription or homology."


History of the gene: 1869-1970:
1869 - The chemical material DNA is discovered in cells but its real functions are not known.
1909 - The term "gene" is first used and the chemical composition of DNA is discovered.
1920 - Chromosomes are proposed as the mechanism by which inherited characteristics are passed on.
1944 - DNA is first connected to the inheritance of traits.
1951 - The first sharp X-ray diffraction photographs of DNA are obtained.
1953 - Crick and Watson describe the structure of DNA.
1956 - DNA is made artificially.
1966 - DNA is found to be present not only in chromosomes but also in the mitochondria.
1969 - The first single gene is isolated.
1970 - The first artificial gene is made.
The gene:
"A gene is a sequence (a string) of bases. It is made up of combinations of A, T, C, and G. These unique combinations determine the gene's function, much as letters join together to form words. Each person has thousands of genes -- billions of base pairs of DNA or bits of information repeated in the nuclei of human cells --which determine individual characteristics (genetic traits)."
"Structurally, a basic unit of hereditary material; an ordered sequence of nucleotide bases that encodes a product (this product could be just RNA like rRNA or finally coding for a protein). The gene includes, however, regions preceding and following the coding region (5' UTR and 3' UTR) as well as (in eukaryotes) intervening sequences (introns) between individual coding segments (exons)."

"a DNA segment that contributes to phenotype/function. In the absence of demonstrated function a gene may be characterized by sequence, transcription or homology". The overwhelming majority of objects named by HGNC are in this category(from: HUGO Gene Nomenclature Committee ; Human Genome Organization)"

" a unit of inheritance; a working subunit of DNA. Each of the body's 20,000 to 25,000 genes contains the code for a specific product, typically, a protein such as an enzyme. "
(Revised: October 2004) (NIH glossary; http://www.accessexcellence.com/AE/AEPC/NIH/gene27.html#gene)

"Genes .... are working subunits of DNA. DNA is a vast chemical information database that carries the complete set of instructions for making all the proteins a cell will ever need. Each gene contains a particular set of instructions, usually coding for a particular protein."
(www.accessexcellence.com)

"unit of hereditary information that occupies a fixed position (locus) on a chromosome. Genes achieve their effects by directing the synthesis of proteins."
(http://www.britannica.com/)

" The functional and physical unit of heredity passed from parent to offspring. Genes are pieces of DNA, and most genes contain the information for making a specific protein. "
(from National Human Genome Institute; glossary of genetic terms; www.nhgri.nih.gov/DIR/VIP/Glossar)
"It is because a gene is a segment of DNA (on a specific site on a chromosome) that is responsible for the physical and inheritable characteristics or phenotype of an organism. It also specifies the structure of a protein, and an RNA molecule. "
http://www.biology-online.org/dictionary/Gene

"A gene is a DNA sequence that is transcribed to produce a functional product."
http://sandwalk.blogspot.com/2007/01/what-is-gene.html

Posted in: Genetics