What Makes a Man a Man?


Quick Answer

Gender is determined by the presence or absence of the Y chromosome. The Y chromosome carries the genes that are needed to override the body's biological default, which is female development, resulting in the development of the male reproductive system.

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Full Answer

The human genome consists of 23 pairs of chromosomes, with genetic information from each parent carried by one chromosome within each pair. The X and Y chromosomes, also known as sex chromosomes, determine the biological gender of an individual. Chromosomes consists of DNA that have been tightly packed into thread-like structures. While women are able to pass on only the X chromosome to their offspring, men are able to pass on either the X or the Y needed to begin male development.

While each pair of chromosomes are superficially indistinguishable, the X and Y chromosomes are different. The Y chromosome is much smaller than the X, and while these chromosomes do make up a pair, their ability to recombine genetic material is limited. The majority of the genetic information stored in the Y chromosome is passed from father to son in a manner not unlike asexual reproduction. The limited recombination of genetic material between the X an Y chromosome means that deleterious mutations cannot be independently selected against.

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