Which mechanism contributes to the independent assortment of chromosomes during meiosis?

• A. Crossing over
• B. Mitosis
• C. DNA replication
• D. Independent assortment of homologous chromosomes

Answer: (D)

Chromosome alignment and separation during meiosis I drive independent assortment. When homologous chromosome pairs line up at the metaphase plate, their orientation is random with respect to maternal and paternal origin. As the pairs are pulled apart in anaphase I, each gamete receives a mix of chromosomes from both parents, creating many possible combinations. This random distribution of whole chromosomes is what generates genetic variety among offspring.

Crossing over, while another source of variation, occurs earlier in prophase I and reshuffles alleles between homologs on the same chromosomes rather than distributing whole chromosomes independently. Mitosis involves different processes for somatic cell division and does not produce this random segregation of homologous pairs. DNA replication happens before meiosis to duplicate DNA but does not by itself cause the random separation of chromosomes into gametes.