Which process increases genetic variation via crossing over?

• A. Meiosis
• B. Mitosis
• C. Fertilization
• D. Binary fission

Answer: (A)

Crossing over increases genetic variation through recombination that happens during meiosis. In prophase I, homologous chromosomes pair up and exchange small DNA segments. This shuffles alleles and creates recombinant chromosomes, so the gametes produced carry new allele combinations rather than just the parental ones. That additional mixing boosts genetic diversity beyond what would come from independent assortment alone.

The other processes don’t involve this kind of chromosome pairing and exchange. Mitosis copies and separates sister chromatids without swapping material between homologs, so no crossing over occurs. Fertilization mixes genetic material from two gametes but the key exchange that creates new gene combinations happens earlier, during meiosis. Binary fission is an asexual process in which a single organism duplicates itself without homologous chromosome pairing or crossing over.