Replication Error

Replication Error

Replication Error - a mistake that occurs when DNA sequences duplicate before cell division. Replication errors are accountable for CHROMOSOMAL DISORDERS such as AUTOSOMAL TRISOMY, in which a GAMETE (also called a sex cell or germ cell) receives two copies of a CHROMOSOME instead of the normal single copy. Gametes, which are haploid cells, each carry one-half the complement of chromosomes so when they unite to form the ZYGOTE that will become a new human being, the zygote contains the full complement of genetic material. With a replication error such as an autosomal trisomy, the zygote receives an extra chromosome two copies from one gamete and one copy from the other gamete. The result is a chromosomal disorder such as DOWN SYNDROME. Replication errors also may have harmless consequences when they occur in DNA sequences that do not encode structural or regulatory sequences of gene activity.

See also MUTATION; VARIATION.

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Genetics and Molecular Medicine

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