Question

parents can pass on chromosomes to their children that are different than their own when the new gene combinations are created by
a crossing over of sister chromatids during meiosis.
b crossing over of sister chromatids during mitosis.
c crossing over of homologous chromosomes during mitosis.
d crossing over of homologous chromosomes during meiosis.

Explanation:

To solve this, we analyze each option:

• Option A: Sister chromatids are identical, so crossing over between them doesn't create new gene combinations. Also, the key process for genetic variation in gametes (passed to children) is meiosis, but this part is incorrect due to sister chromatids.
• Option B: Mitosis is for cell growth/repair, not for producing gametes. Also, sister chromatids crossing over in mitosis is not a source of new gene combinations for offspring.
• Option C: Mitosis doesn't produce gametes, and crossing over of homologous chromosomes doesn't occur in mitosis.
• Option D: During meiosis, homologous chromosomes (not sister chromatids) cross over, exchanging genetic material. This creates new gene combinations in the chromosomes that parents can pass to children (via gametes produced in meiosis).

Answer:

D. crossing over of homologous chromosomes during meiosis.