What are homologous chromosomes?

• A. Chromosomes that have the same sequence of genes and the same structure
• B. Chromosomes that carry the same alleles
• C. Chromosomes that are identical copies created during mitosis
• D. Chromosomes that pair only during mitosis

Answer: (A)

Homologous chromosomes are the paired chromosomes that carry the same genes in the same order and have a similar structure, with one chromosome inherited from each parent. They may carry different alleles for those genes, so they are not necessarily identical copies. They are not identical copies produced during DNA replication (those are sister chromatids). They pair up during meiosis I to align and allow recombination and proper segregation, not during mitosis. This is why the best description is chromosomes that share the same sequence of genes and same overall structure.