How do mitosis and meiosis differ in chromosome number, alignment, and potential for genetic variation?

• A. Mitosis yields two haploid cells; Meiosis yields two diploid cells.
• B. Mitosis involves crossing over and independent assortment; Meiosis does not.
• C. Mitosis yields two genetically identical diploid cells; Meiosis yields four haploid cells with genetic variation due to recombination and independent assortment.
• D. Mitosis occurs in germ cells; Meiosis in somatic.

Answer: (C)

The key idea is how the two divisions change chromosome number, how chromosomes line up, and how genetic variation arises. In mitosis, after DNA replication there is a single division that produces two daughter cells, both diploid and genetically identical to the parent (apart from rare mutations). Chromosomes separate as sister chromatids, lining up as individual chromosomes at the metaphase plate, with no reshuffling of alleles, so variation is minimal. In meiosis, there are two divisions, yielding four haploid cells. Homologous chromosomes pair and form tetrads during prophase I, enabling crossing over (recombination) that creates new allele combinations. They align as pairs (not single chromosomes) at the metaphase plate in meiosis I, and independent assortment of maternal and paternal homologs during anaphase I further increases variation. Meiosis II then separates sister chromatids, but the genetic shuffling has already occurred. So the best description is that mitosis makes two genetically identical diploid cells, while meiosis makes four haploid cells with genetic variation due to recombination and independent assortment.