Final answer:
Male and female human gametes each have 23 chromosomes. Male gametes may have an X or Y chromosome determining the zygote's sex, while female gametes contain only an X chromosome. Gametes join during fertilization to form a diploid zygote, whose genotype expresses through physical and behavioral traits in its phenotype.
Step-by-step explanation:
The genetic constitution of human gametes involves 23 chromosomes. Male gametes, or sperm, can carry either an X or Y chromosome, contributing to the determination of the offspring's sex, while female gametes, or eggs, contain only the X chromosome.
Human body cells are diploid (2n), carrying a complete set of 46 chromosomes, 23 from each parent. In contrast, gametes are haploid (n), containing just one set of chromosomes. When an egg and sperm combine during fertilization, they form a zygote, which has a full complement of chromosomes and is again diploid. The zygote's genotype, which includes both autosomal chromosomes and sex chromosomes, determines its phenotype, a blend of inherited physical and behavioral traits.
Each gamete's single set of 23 chromosomes includes autosomes and one sex chromosome. The male gamete determines the sex of a zygote by contributing an X (resulting in a female) or Y chromosome (resulting in a male), while the female gamete contributes an X chromosome. Genes within these chromosomes express traits like hair color, eye color, and countless other characteristics through the coding of specific proteins.