Homologous describes which of the following?

• A. Chromosomes that are identical in size and gene order
• B. Traits of organisms are due to sharing a common ancestor; Same structure different function
• C. A type of allele that masks another
• D. A process of cell division that doubles chromosome number

Answer: (B)

Homologous describes similarity that comes from a common ancestor. Structures or traits that are homologous share an origin and a similar plan, even when they end up serving different functions. For example, the bone structure in forelimbs across mammals is similar, but the limbs are used for different tasks like grasping, swimming, or flying. In genetics, homologous chromosomes carry the same genes in the same order, one from each parent, though the alleles may differ between the two chromosomes. This idea of shared origin and preserved structure underlies the description in the choice. The other options either push too far (calling chromosomes identical in size and gene order) or describe unrelated concepts (dominance of alleles or a cell division process that doubles chromosome number).