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From Biology-Online Dictionary | Biology-Online Dictionary
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noun, plural: chromosomes

A structure within the cell that bears the genetic material as a threadlike linear strand of DNA bonded to various proteins in the nucleus of eukaryotic cells, or as a circular strand of DNA (or RNA in some viruses) in the cytoplasm of prokaryotes and in the mitochondrion and chloroplast of certain eukaryotes.


In eukaryotes, the chromosomes appear as threadlike strand that condense into thicker structures and aligns on the metaphase plate during mitosis. Humans normally have 23 pairs of chromosomes, each with a characteristic length and banding pattern. Chromosomes occur in pairs (in most somatic cells) since one member of each pair comes from the mother and the other from the father. In most prokaryotes, the chromosome is usually a circular strand of DNA; hence, the entire genome is carried on only one chromosome. In viruses, the chromosome may appear as short linear or circular structure containing the DNA or RNA molecule often lacking any structural proteins.

Word origin: from the Greek chroma = color + soma = body.

Related forms: chromosomal (adjective).
Related terms: w chromosome, marker chromosome, ring chromosome, Y chromosome, X chromosome, lampbrush chromosome, homologous chromosome, chromosome puffs, chromosome rosette, chromosome satellite, Christchurch chromosome.