Question

question 5 of 25
which sentence describes how crossing over increases genetic variation?
a. it combines gametes from different individuals.
b. it increases the number of genes in a chromosome that can be inherited.
c. it increases the number of possible chromosome combinations that can occur in offspring.
d. it increases the number of possible allele combinations that can occur on a single chromosome.

Explanation:

Crossing over occurs during meiosis. Homologous chromosomes exchange genetic material (alleles). This recombination on a single chromosome leads to new allele combinations. Option A is about fertilization (combining gametes from different individuals), not crossing - over. Option B: Crossing - over does not increase the number of genes (just recombines alleles). Option C: Independent assortment (not crossing - over) mainly affects chromosome combinations in offspring. So, crossing - over specifically increases allele combinations on a single chromosome.

Answer:

D. It increases the number of possible allele combinations that can occur on a single chromosome.