Question

which event is likely to decrease the genetic variation in a population?
a. failure of non - sister chromatids to cross over during meiosis
b. independent assortment of chromosomes during metaphase i
c. homologous chromosome pairs lining up randomly before being pulled apart in meiosis i
d. zygotes receiving a unique set of chromosomes from each gamete

Explanation:

• Option A: Crossing - over between non - sister chromatids during meiosis creates new combinations of alleles. If this fails to occur, there is less opportunity for new genetic combinations, which is likely to decrease genetic variation.
• Option B: Independent assortment of chromosomes during metaphase I leads to different combinations of maternal and paternal chromosomes in gametes, increasing genetic variation.
• Option C: Random lining up of homologous chromosome pairs (a part of independent assortment) before being pulled apart in meiosis I also contributes to genetic variation by creating different gamete genotypes.
• Option D: Zygotes receiving a unique set of chromosomes from each gamete (due to processes like independent assortment and crossing - over in gamete formation) increases genetic variation as each zygote has a distinct genetic makeup.

Answer:

A. Failure of non - sister chromatids to cross over during meiosis