Human sperm and oocytes are substantially different in all of the following aspects EXCEPT:

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11ecba2d_0fd4_0370_a3bf_ebb4e2d2e164_MD0008_00 Ploidy is defined as the number of homologous chromosome sets in the nucleus of a cell. In the human body, with the exception of sperm and egg cells (reproductive cells), nucleated cells are diploid and known as somatic cells. Somatic cells have 46 individual chromosomes that appear as 23 pairs. Each somatic cell has two sets/copies (2N) of each chromosome, these include 22 pairs of homologous chromosomes (autosomes) and 1 pair of sex chromosomes. In contrast, mature egg and sperm are both haploid (1N) because they each contain 22 (unpaired) autosomes and 1 sex chromosome, resulting in 23 chromosomes. During fertilization, the egg and sperm form a zygote with a nucleus containing the full complement of 46 chromosomes. These 46 chromosomes are found in pairs, and in each pair one chromosome comes from the mother and one comes from the father. Accordingly, egg and sperm cells are similar in ploidy as they both are haploid cells and contribute the same number of chromosomes to a zygote. (Choice A) Sperm are the smallest cells in the human body and mostly contain a nucleus, an acrosome, mitochondria, and a negligible amount of cytoplasm. In contrast, the egg is the largest human cell and has organelles and a large amount of cytoplasm. (Choice B) During gestation, the germ cells of the embryo first undergo numerous mitotic divisions to proliferate, after which they are primed for meiosis, a type of cell division that results in the formation of gametes. However, the testes of newborn boys contain only immature germ cells (spermatogonia) that have not progressed beyond the mitotic stages. These immature spermatogonia begin to undergo meiosis at puberty (early teen years) when the gonads mature. In contrast, newborn girls have primary oocytes arrested at prophase of meiosis I and remain in this state until ovulatory cycles begin at puberty. (Choice D) In the adult male, millions of sperm cells are produced daily after the onset of puberty. However, females are born with their full complement of oocytes, and only a few mature during each menstrual cycle, which occurs approximately once every 28 days. Educational objective: Egg and sperm cells are haploid cells that contribute an equal number of chromosomes to a zygote during fertilization.

Human Sperm and Oocytes Are Substantially Different in All of the Following