A gene is a sequence o DNA or RNA that codes for a molecule that has a function. In gene expression, the DNA is first copied intae RNA. The RNA can be directly functional or be the intermediate template for a protein that performs a function. The transmission o genes tae an organism's affspring is the basis o the inheritance o phenotypic traits. Thir genes mak up different DNA sequences cried genoteeps. Genoteeps alang wi environmental an developmental factors determine whit the phenoteeps will be. Maist biological traits are unner the influence o polygenes (mony different genes) as well as gene–environment interactions. Some genetic traits are instantly veesible, sic as ee colour or nummer o limbs, an some are nae, sic as bluid teep, risk for speceefic diseases, or the thoosands o basic biochemical processes that constitute life.
Genes can acquire mutations in thair sequence, leadin tae different variants, kent as alleles, in the population. Thir alleles encode slichtly different versions o a protein, that cause different phenoteepical traits. Uissage o the term "haein a gene" (e.g., "guid genes," "hair colour gene") teepically refers tae conteening a different allele o the same, shared gene. Genes evolve due tae naitural selection or survival o the fittest o the alleles.
The concept o a gene conteenas tae be refined as new phenomena are diskivert. For ensaumple, regulatory regions o a gene can be faur remuived frae its codin regions, an codin regions can be split intae several exons. Some viruses store thair genome in RNA instead o DNA an some gene products are functional non-codin RNAs. Tharefore, a braid, modren wirkin defineetion o a gene is ony discrete locus o heritable, genomic sequence that affect an organism's traits bi bein expressed as a functional product or bi regulation o gene expression.
- Gericke, Niklas Markus; Hagberg, Mariana (5 December 2006). "Definition of historical models of gene function and their relation to students' understanding of genetics". Science & Education. 16 (7–8): 849–881. Bibcode:2007Sc&Ed..16..849G. doi:10.1007/s11191-006-9064-4.
- Pearson H (Mey 2006). "Genetics: what is a gene?". Nature. 441 (7092): 398–401. Bibcode:2006Natur.441..398P. doi:10.1038/441398a. PMID 16724031.
- Pennisi E (Juin 2007). "Genomics. DNA study forces rethink of what it means to be a gene". Science. 316 (5831): 1556–1557. doi:10.1126/science.316.5831.1556. PMID 17569836.
- Johannsen, W. (1905). Arvelighedslærens elementer ("The Elements o Heredity". Copenhagen). Rewritten, enlairged an translatit intae German as Elemente der exakten Erblichkeitslehre (Jena: Gustav Fischer, 1905; Scanned full text. Archived 2009-05-30 at the Wayback Machine