Which process is described as the exchange of genetic material between homologous chromosomes during the first prophase of meiosis?

Which process is described as the exchange of genetic material between homologous chromosomes during the first prophase of meiosis?

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

Answer: (A)

Crossing over is the exchange of genetic material between homologous chromosomes during prophase I of meiosis. When homologs pair up in synapsis, non-sister chromatids within each tetrad can break and rejoin, swapping segments and creating recombinant chromatids with mixed maternal and paternal alleles. This occurs at sites called chiasmata and is driven by the meiotic recombination machinery that processes double-strand breaks. The outcome is greater genetic variation in gametes, a hallmark of meiosis. Nondisjunction is about chromosome separation errors, Zygote is a fertilized cell, and recombination is the broader concept that includes crossing over but doesn’t specify the physical exchange during prophase I.

Crossing over is the exchange of genetic material between homologous chromosomes during prophase I of meiosis. When homologs pair up in synapsis, non-sister chromatids within each tetrad can break and rejoin, swapping segments and creating recombinant chromatids with mixed maternal and paternal alleles. This occurs at sites called chiasmata and is driven by the meiotic recombination machinery that processes double-strand breaks. The outcome is greater genetic variation in gametes, a hallmark of meiosis. Nondisjunction is about chromosome separation errors, Zygote is a fertilized cell, and recombination is the broader concept that includes crossing over but doesn’t specify the physical exchange during prophase I.