Describe how genetic recombination occurs during meiosis.

• A. During prophase II, sister chromatids exchange DNA to increase diversity.
• B. Random fertilization leads to diversity.
• C. Crossing over between homologous chromosomes during prophase I exchanges alleles, increasing genetic diversity.
• D. Mutation during DNA replication creates diversity.

Answer: (C)

Genetic recombination in meiosis mainly comes from crossing over between homologous chromosomes during prophase I. When the homologous chromosomes pair up, they form a tetrad, and the non-sister chromatids exchange segments. This exchange shuffles maternal and paternal alleles between the chromatids, producing recombinant chromosomes with new allele combinations. As a result, the gametes that form after meiosis carry diverse genetic material, increasing variation in offspring.

This process happens during prophase I, facilitated by the pairing and the crossover points called chiasmata. The amount of recombination between genes tends to depend on how far apart they are on the chromosome—the farther apart, the more likely a crossover will occur between them.

The other ideas don’t describe recombination itself. Crossing over between sister chromatids would not generate new allele combos, while random fertilization adds diversity from which gametes combine, not from recombination. Mutation during DNA replication can create new alleles but is separate from the exchange of chromosome segments.