Which of the following are sources of genetic variation during meiosis?

• A. Crossing over, independent assortment
• B. Crossing over, DNA replication
• C. DNA replication, independent assortment
• D. Disjunction, crossing over

Answer: (A)

Verified step by step guidance

1. Understand that genetic variation is crucial for evolution and adaptation, and meiosis is a key process that increases genetic diversity.
2. Recognize that 'crossing over' occurs during prophase I of meiosis, where homologous chromosomes exchange genetic material, leading to new combinations of alleles.
3. Identify 'independent assortment' as the process during metaphase I where homologous chromosome pairs are distributed randomly into daughter cells, contributing to genetic variation.
4. Clarify that 'DNA replication' occurs before meiosis begins, during the S phase of the cell cycle, and does not directly contribute to genetic variation during meiosis itself.
5. Note that 'disjunction' refers to the separation of homologous chromosomes or sister chromatids during anaphase I or II, respectively, and while it is crucial for proper chromosome segregation, it does not introduce new genetic variation.