What is the role of haploid cells in sexual reproduction?

• A. They fuse during fertilization to restore the diploid chromosome number.
• B. They are produced by mitosis to maintain chromosome number.
• C. They have two sets of chromosomes.
• D. They are not involved in reproduction.

Answer: (D)

Haploid cells in sexual reproduction are the gametes that carry a single set of chromosomes. Their main role is to fuse with another haploid gamete during fertilization to restore the diploid chromosome number in the zygote. This joining combines the paternal and maternal chromosome sets, producing a cell with two complete sets that can develop into a new individual. These haploid gametes are produced by meiosis, not mitosis, which is why genetic variation arises from crossing over and independent assortment. For example, human gametes have 23 chromosomes each, and when sperm and egg unite, a 46-chromosome zygote forms. The idea that haploid cells aren’t involved in reproduction isn’t correct, because they are essential to forming the diploid organism.