Which two processes contribute to genetic variation in meiosis?

• A. Crossing over only
• B. Crossing over in prophase I and independent assortment in metaphase I
• C. DNA replication and transcription
• D. Cytokinesis and mitosis

Answer: (B)

During meiosis, genetic variation mainly comes from two events: crossing over in prophase I and independent assortment in metaphase I. Crossing over involves homologous chromosomes exchanging equal segments, so alleles are shuffled between chromosomes and new combinations appear that weren’t present in the parent. This recombination happens as the homologues pair up in prophase I. Independent assortment occurs when these chromosome pairs line up at the cell’s equator during metaphase I and orient themselves randomly; which member of each pair goes to a given gamete is independent of the others, producing many possible combinations of maternal and paternal chromosomes.

Together, these processes generate the diverse set of gametes that can fertilize to form genetically varied offspring. The other options don’t capture both mechanisms: crossing over alone ignores the random distribution of chromosomes, while DNA replication or transcription aren’t the processes that create meiotic variation, and cytokinesis with mitosis describes different stages or processes that don’t lead to variation in meiosis.