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Saturday 1 May 2004

Definition: A gene is an ordered sequence of nucleotides located in a particular position (locus) on a particular chromosome that encodes a specific functional product (the gene product, i.e. a protein or RNA molecule). It includes regions involved in regulation of expression and regions that code for a specific functional product. See gene expression, allele.

Human genome comprises between 20000 and 29000 genes.


- housekeeping genes
- cancer genes

  • oncogenes
  • tumor suppressor genes

Pathology (genic anomalies)

- quantitative genic anomalies

  • genic overexpression
    • genic amplification
    • translocation downstream of an active promoter
    • numerical chromosomal anomalies (trisomies, tetrasomies)
  • genic underexpression
    • genic inactivation
      • numerical chromosomal anomalies (deletions)
      • mutations of gene promoter
      • methylation of gene promoter

- qualitative genic anomalies (genic mutation)

  • proteic loss of function
    • genic deletion
    • point mutation
  • genic activation (proteic gain of function)
  • fusion genes (fusion proteins)


The term coined by Johannsen (1909) for the fundamental physical and functional unit of heredity. The word gene was derived from De Vries’ term pangen, itself a derivative of the word pangenesis which Darwin (1868) had coined.

See also

- cancer genes

  • oncogenes
  • tumor suppressor genes


- Carlson EA. Defining the gene: an evolving concept.
Am J Hum Genet. 1991 Aug;49(2):475-87. PMID: 1867208