The cells that contain 23 single chromosomes are known as haploid cells. In humans, these haploid cells are primarily represented by gametes, which are the sperm and egg cells. Each gamete carries one set of chromosomes, totaling 23 individual chromosomes. This is half the number of chromosomes found in diploid cells, which contain 46 chromosomes, or 23 pairs.
During sexual reproduction, when a sperm cell fertilizes an egg cell, the two haploid cells combine to form a diploid zygote with 46 chromosomes. This process is crucial for maintaining the species’ chromosome number across generations, as fertilization restores the diploid state after the union of two haploid cells.