Question

gametes are not exact copies of body cells due to gene exchanges such as crossing - over,
a true
b false

Explanation:

Gametes are formed through meiosis. During prophase I of meiosis, crossing - over occurs. Crossing - over is the exchange of genetic material between homologous chromosomes. This genetic recombination leads to new combinations of genes in the gametes. Body cells (somatic cells) are formed through mitosis, which produces cells that are exact copies (genetically identical, barring mutations) of the parent cell. Since gametes have genetic variation due to crossing - over (and also independent assortment of chromosomes), they are not exact copies of body cells.

Answer:

A. True