Which of the following statements about crossing over is TRUE?

It occurs only between genes that are heterozygous.

It occurs during prophase I and prophase II of meiosis.

It occurs only in some chromosomes.

It results in reduced genetic variation among gametes.

None of these choices are correct.

Answer: None of the choices are true.

Explanation:

Crossing over can be defined as the swapping of the genetic material which occurs in the germ line.

When the sperm and ovum combine together during the process of meiosis then the paired chromosomes from each of the parent align in such a way that the similar DNA sequence form the paired chromosomes cross over on each other.

The crossing over results in the genetic variation.

The correct answer is None of these choices are correct.

Explanation:

Crossing over doesn't occur only between heterozygous genes, it also doesn't happen only in some chromosomes and it never reduces de variation, otherwise, the crossing over is one of the main causes of variation among species.