What is meant by homologous chromosomes?

Homologous chromosomes are pairs of chromosomes that consist of one chromosome from each parent. These chromosomes are similar in shape, size, and genetic content, which allows them to pair up during meiosis. While they carry genes for the same traits, the variations in those genes that come from each parent may result in different alleles. This pairing is crucial during sexual reproduction because it ensures genetic diversity and proper segregation of chromosomes.

In the context of the other choices, chromosomes from the same parent that are identical would refer to sister chromatids, not homologous chromosomes. Chromosomes having different genes does not accurately describe the nature of homologous chromosomes, since they typically carry genes for the same traits, albeit potentially in different forms (alleles). Lastly, chromosomes that exist in different species do not meet the definition of homologous chromosomes, as those would not constitute pairs in terms of genetic similarity and pairing during meiosis.