IGCSE Biology – Human Reproduction Practice Test

Human gametes, which include sperm and egg cells, contain 23 chromosomes. This number is significant because these cells are haploid, meaning they have half the number of chromosomes compared to somatic (body) cells, which are diploid and contain 46 chromosomes.

During fertilization, when a sperm cell fuses with an egg cell, the two sets of chromosomes come together to form a diploid zygote with a total of 46 chromosomes, restoring the full number. Therefore, the presence of 23 chromosomes in gametes is essential for maintaining the correct chromosomal balance across generations in sexually reproducing organisms. This reduction in chromosome number ensures genetic diversity while preventing the chromosome number from doubling with each generation.