homologous

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homologous A term applied to organs or chromosomes. An organ of an animal is said to be homologous with that of another when both are thought to have the same evolutionary origin, although their functions may differ widely. Homology is generally deduced from similarity of structure and/or position of the organ relative to other organs, seen particularly during embryonic development; e.g., in the plant kingdom the fertilization of the lower plants (e.g. Bryophyta) is often effected by motile male gametes; this is homologous to the male gamete of Spermatophytes which is non-motile and transferred in the pollen grain. Homologous chromosomes are those that contain identical linear sequences of genes, and which pair during meiosis. Each homologue is therefore a duplicate of one of the chromosomes contributed by one of the parents; and each pair of homologous chromosomes is normally identical in shape and size.

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