What term describes exchange of genetic material between homologous chromosomes during the first prophase of meiosis?

• A. Crossing over
• B. Recombination
• C. Nondisjunction error
• D. Karyotype

Answer: (A)

During the first prophase of meiosis, homologous chromosomes pair up and non-sister chromatids exchange segments at sites called chiasmata. This exchange is known as crossing over. It physically swaps pieces of DNA between homologs, producing new combinations of alleles on each chromosome and increasing genetic variation in gametes. While recombination describes the resulting new allele combinations, the specific process described here is crossing over. Nondisjunction refers to an error in chromosome separation, and a karyotype is just a snapshot of chromosome number and structure, not the exchange of genetic material.