How does meiosis contribute to genetic variation?

• A. Crossing over in prophase I and independent assortment create new combinations of alleles
• B. Mitosis creates genetic variation
• C. Random mutation during replication only
• D. Fusion of gametes determines variation

Answer: (A)

Meiosis contributes to genetic variation through the shuffling of alleles in two key ways. In prophase I, homologous chromosomes pair up and non-sister chromatids exchange segments in a process called crossing over. This creates chromatids with new combinations of alleles that weren’t together on either chromosome before. Later, the way chromosome pairs align and separate during meiosis I is random, so the mix of maternal and paternal chromosomes that end up in a gamete varies each time. Together, crossing over and independent assortment generate many different possible gamete genotypes, and when fertilization occurs, combining these gametes gives even more genetic diversity. Mitosis doesn’t involve crossing over or this random assortment, so it doesn’t produce the same level of variation. While mutations or fertilization also influence variation, the specific processes inside meiosis that create new allele combinations are crossing over and independent assortment.