Definition

Noun: * In genetics, a cistron is a segment of DNA that codes for a specific polypeptide chain (a protein or part of a protein). It is the functional unit of heredity, encompassing not only the coding sequences (exons) but also the regulatory regions and non-coding intervening sequences (introns). Historically, the term was used to define a gene based on its function in a specific test.

Examples

• Noun:
  • The scientist mapped the specific cistron responsible for the enzyme's production.
  • Mutations within this cistron can lead to a loss of protein function.
  • In classical genetics, a cistron was defined operationally by the complementation test.

Advanced Usage

• The term cistron is largely synonymous with the modern molecular definition of a gene, especially when referring to a protein-coding sequence. It emphasizes the gene as a functional unit.
• It is used to distinguish a functional genetic unit from a mutational or recombination unit (a muton or recon, respectively).

Variants and Related Words

• Gene (n): The more common modern term for the fundamental physical and functional unit of heredity. While often used interchangeably with cistron, "gene" can have broader connotations.
• Exon (n): The coding segments of a cistron or gene that are expressed in the final protein product.
• Intron (n): The non-coding intervening sequences within a cistron or gene that are removed during RNA processing.

Synonyms

• Gene
• Genetic factor (historical)
• Hereditary unit

Related Phrases

• Cistron map: A genetic map showing the location and order of cistrons.
• Polycistronic mRNA: A single messenger RNA molecule that encodes multiple proteins (multiple cistrons), common in prokaryotes.

Noun

1. (genetics) a segment of DNA that is involved in producing a polypeptide chain; it can include regions preceding and following the coding DNA as well as introns between the exons; it is considered a unit of heredity
   • genes were formerly called factors