The sex of humans and other mammals, as regulated by the presence or absence of the Y chromosome. Humans have 22 sets of non-sex chromosomes and one set of sex chromosomes. Females have two X chromosomes, while males have one X and a small Y chromosome. The sex chromosomes, X and Y, though paired in males, are different from each other, and the presence of a Y chromosome is necessary for male sexual characteristics to develop.
The identification of the gender of an animal or human with an ambiguous physical appearance or ambiguous genitalia. In colloquial speech, this process is sometimes referred to as “sex testing.”
The factors that dictate biological sex are primarily determined by the sex chromosomes within a person’s cells: females have two X chromosomes, while males have one X and one Y chromosome. Early in embryonic growth, these chromosomes influence the formation of specific reproductive organs: testes in males and ovaries in females. In males, the testes generate hormones that result in the development of a male reproductive system, including a penis. In females, the lack of these male hormones guides development in a different direction, leading to the creation of fallopian tubes, a uterus, and a vagina. During puberty, another wave of hormones from the reproductive organs triggers the emergence of secondary sexual traits, such as facial hair in males, breast development in females, and pubic hair in both genders.
Sometimes, abnormalities can happen in the process of sex determination, leading to unclear or ambiguous sexual characteristics. In some instances, individuals may have an unusual set of sex chromosomes, resulting in incomplete development of traits associated with one gender. The extremely rare condition of true hermaphroditism involves the presence of both ovarian and testicular tissue in the body.
Male sex cells, or sperm, come in two varieties: one type carries the X sex chromosome among its 23 chromosomes, while the other type carries the Y sex chromosome. When the female sex cell, or egg, is fertilized by a sperm containing the X chromosome, the result is a female offspring. Conversely, when the egg is fertilized by a sperm bearing the Y chromosome, the offspring is male. Therefore, the sex of the offspring is determined by the contribution of the male.