 What is a Gene? |
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Definitions of what a gene is are surprisingly inconsistent. Here is a brief listof definitions from various editorial/professional resources and organizations. The Human Genome Sequencing Consortium published an update on the whole genome sequence of Homo Sapiens in 2004 and concluded that there are between 20,000 and 25,000 structural genes. This is lower than the lowest estimate of the gene sweepstake given as 27,462 and is lower than the 2001 estimated number of 35,000 genes when the first draft sequence of the human genome was published. (Reference: Human Genome Sequencing Consortium, I. (2004). "Finishing the euchromatic sequence of the human genome." Nature 431(7011): 931-945.) UPDATE: 'The Human Genome 2012: 18,451 RNA genes, 11,224 pseudogenes, 20,687 protein coding genes, an average of 6.3 splice variants per gene, gene sequences cover 2.94% of the genome, exon sequences cover 1.22% of the genome' (ENCODE, Nature.com) Gene: 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) Gene: 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) gene: 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/) gene defined: 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; http://www.genome.gov/Glossary/) Main Entry: gene | Pronunciation: 'jEn | Function: noun a specific sequence of nucleotides in DNA or RNA that is located in the germ plasm usually on a chromosome and that is the functional unit of inheritance controlling the transmission and expression of one or more traits by specifying the structure of a particular polypeptide and especially a protein or controlling the function of other genetic material -- called also determinant, determiner, factor ( Merriam Webster Dictionary; at Harvard Medical School www.intelihealth.com) Home |