Sex linkage
Sex linkage
Sex linkage (/sɛks lɪŋkɪdʒ/), in genetics, refers to the phenomenon where the expression of a trait is determined by the sex chromosomes. The term was first coined by Thomas Hunt Morgan, an American evolutionary biologist, geneticist, and embryologist.
Etymology
The term "sex linkage" is derived from the words "sex", referring to the biological and physiological characteristics that define men and women, and "linkage", which in genetics refers to the tendency of DNA sequences that are close together on a chromosome to be inherited together.
Related terms
- X-linked: Refers to the pattern of inheritance for genes located on the X chromosome.
- Y-linked: Refers to the pattern of inheritance for genes located on the Y chromosome.
- Z-linked: Refers to the pattern of inheritance for genes located on the Z chromosome in species with ZW sex-determination system.
- Autosomal: Refers to the chromosomes that are not sex chromosomes.
Sex linkage in humans
In humans, sex linkage primarily refers to genes located on the X and Y chromosomes, the two sex chromosomes. Men have one X and one Y chromosome (XY) and women have two X chromosomes (XX). Therefore, a trait that is sex-linked can appear more frequently in one sex than in the other.
For example, color blindness and hemophilia are X-linked recessive traits. This means that they are more common in males, because males have only one X chromosome and therefore only one copy of the gene in question. Females, on the other hand, have two X chromosomes and therefore two copies of the gene. If one copy is defective, the other can often compensate.
See also
External links
- Medical encyclopedia article on Sex linkage
- Wikipedia's article - Sex linkage
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