In meiosis, how does independent assortment contribute to genetic variation?

In meiosis, how does independent assortment contribute to genetic variation?

• A. Homologous chromosomes orient randomly during metaphase I, producing diverse combinations of maternal and paternal chromosomes in gametes.
• B. Crossing over alone generates variation.
• C. Independent assortment occurs only in mitosis.
• D. Variation arises only from mutation, not from meiosis.

Answer: (A)

The main concept is that random orientation of homologous chromosome pairs during meiosis I creates different combinations of maternal and paternal chromosomes in gametes. As pairs line up on the metaphase plate, which member of each pair goes to each daughter cell is independent and unpredictable. This means the assortment of paternal or maternal chromosomes received by a gamete varies, producing many possible genetic combinations. If there are n chromosome pairs, there are 2^n possible gamete chromosome sets from independent assortment alone (humans have 2^23, over 8 million combinations), and this variety is further expanded when crossing over during prophase I shuffles alleles between homologs. The other options miss that this source of variation comes from how entire chromosomes are separated, that meiosis—not mitosis—handles this process, and that mutation is another, separate contributor to variation rather than the sole source.

The main concept is that random orientation of homologous chromosome pairs during meiosis I creates different combinations of maternal and paternal chromosomes in gametes. As pairs line up on the metaphase plate, which member of each pair goes to each daughter cell is independent and unpredictable. This means the assortment of paternal or maternal chromosomes received by a gamete varies, producing many possible genetic combinations. If there are n chromosome pairs, there are 2^n possible gamete chromosome sets from independent assortment alone (humans have 2^23, over 8 million combinations), and this variety is further expanded when crossing over during prophase I shuffles alleles between homologs. The other options miss that this source of variation comes from how entire chromosomes are separated, that meiosis—not mitosis—handles this process, and that mutation is another, separate contributor to variation rather than the sole source.