homologous chromosome

A homologous chromosome is one of a pair of chromosomes that share the same genetic structure, but not always the same alleles, for a given characteristic. Found in diploid cells, pairs of homologous chromosomes are composed of one chromosome from the female parent, the other from the male. During meiosis, when gametes (sex cells) are formed, homologous chromosomes undergo a complex process known as crossing over, when strands of the chromosomes (chromatids) break from the original chromosome and exchange places with the other member of the pair. The "reshuffling" gives rise to genetic variation, which together with random mutation is an essential part of evolution.