Which statement best describes a characteristic difference between meiosis and mitosis that contributes to genetic variation?

Which statement best describes a characteristic difference between meiosis and mitosis that contributes to genetic variation?

• A. Meiosis involves crossing over and independent assortment, which mitosis does not.
• B. Mitosis produces four genetically diverse daughter cells.
• C. Meiosis occurs in somatic cells.
• D. Mitosis includes random fertilization.

Answer: (A)

The main idea is that genetic variation comes from meiosis-specific events that shuffle alleles: crossing over and independent assortment. In prophase I, homologous chromosomes pair up and exchange DNA segments, producing chromatids with new combinations of alleles. Then, during metaphase I, the way these homologous pairs line up and separate is random, so the particular mix of maternal and paternal chromosomes that end up in each gamete varies. These processes create a lot of possible genetic combos, which fertilization then combines in new ways. Mitosis doesn’t include crossing over or the random separation of homologous chromosomes, so it generally yields two genetically identical daughter cells. That’s why the statement that best describes the difference is that meiosis involves crossing over and independent assortment, which mitosis does not. The other ideas don’t fit: mitosis doesn’t produce four diverse cells; meiosis occurs in germ cells, not somatic cells; and fertilization is a separate, reproductive event, not a feature of mitosis.

The main idea is that genetic variation comes from meiosis-specific events that shuffle alleles: crossing over and independent assortment. In prophase I, homologous chromosomes pair up and exchange DNA segments, producing chromatids with new combinations of alleles. Then, during metaphase I, the way these homologous pairs line up and separate is random, so the particular mix of maternal and paternal chromosomes that end up in each gamete varies. These processes create a lot of possible genetic combos, which fertilization then combines in new ways.

Mitosis doesn’t include crossing over or the random separation of homologous chromosomes, so it generally yields two genetically identical daughter cells. That’s why the statement that best describes the difference is that meiosis involves crossing over and independent assortment, which mitosis does not. The other ideas don’t fit: mitosis doesn’t produce four diverse cells; meiosis occurs in germ cells, not somatic cells; and fertilization is a separate, reproductive event, not a feature of mitosis.