Sex Chromosomes

We have come a long way in our understanding of sexual dimorphism since 355 BC. In those days, Aristotle suggested that the difference between the two sexes was due to the heat of semen at the time of copulation: hot semen generated males, whereas cold semen made females. Thankfully, we now know a little more about the molecular events of sex determination.

Usually, a woman has two X chromosomes (XX) and a man one X and one Y (XY). However, both male and female characteristics can sometimes be found in one individual, and it is possible to have XY women and XX men. Analysis of such individuals has revealed some of the molecules involved in sex determination, including one called SRY, which is important for testis formation.

Source: NCBI, Genes and Disease (NCBI/NIH)1

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The 23rd pair of chromosomes are two special chromosomes, X and Y, that determine our sex. Females have a pair of X chromosomes (46, XX), whereas males have one X and one Y chromosomes (46, XY).

Source: NCBI, Genes and Disease (NCBI/NIH)2

Introduction: Sex Chromosomes

Males have one X and one Y chromosome in every cell of the body. Females have two X chromosomes in every cell. These cells make up all your tissues and organs, including your skin, heart, stomach, muscles, and brain.

Source: NIH News in Health (NIH)3

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Sex Chromosomes: The homologous chromosomes that are dissimilar in the heterogametic sex. There are the X Chromosome, the Y Chromosome, and the W, Z chromosomes (in animals in which the female is the heterogametic sex (the silkworm moth Bombyx mori, for example)). In such cases the W chromosome is the female-determining and the male is ZZ. (From King & Stansfield, A Dictionary of Genetics, 4th ed)4

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Sex Chromosome: The X or Y chromosome in human beings that determines the sex of an individual. Females have two X chromosomes in diploid cells; males have an X and a Y chromosome. The sex chromosomes comprise the 23rd chromosome pair in a human karyotype.5

Categories for Sex Chromosomes

Category of Sex Chromosome:


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  1. Source: NCBI, Genes and Disease (NCBI/NIH): books/ NBK22246/ 
  2. Source: NCBI, Genes and Disease (NCBI/NIH): books/ NBK22266/ 
  3. Source: NIH News in Health (NIH): issue/ may2016/ feature1
  4. Source: MeSH (U.S. National Library of Medicine)
  5. Source: NCI Thesaurus
  6. ibid.

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Note: This site is for informational purposes only and is not medical advice. See your doctor or other qualified medical professional for all your medical needs.