THE sex-linked inheritance is the name given to the characteristics inherited through the chromosomes sexual.
Generally, the male sex chromosome, represented by the letter Y, carries less information than the female sex chromosome, represented by the letter X.
These two chromosomes, X and Y, have few homologous regions, so there is little gene recombination between them.
the X chromosome has allele genes that correspond on the Y chromosome, these allele genes follow the sex-linked inheritance pattern that can be:
- Inheritance linked only to the X chromosome;
- Inheritance restricted to males;
- Inheritance influenced by sex.
Index
- X-linked inheritance
- Inheritance restricted to males
- Inheritance influenced by sex
- Sex Chromosome Related Diseases
X-linked inheritance
X-linked inheritance occurs when the altered gene is on the X chromosome. This inheritance has maternal origin and pattern recessive.
All humans have at least one X chromosome because they inherit it from their mother. So men are XY and women are XX.
As men have only one X chromosome, all will have the characteristics determined by it, even being in heterozygosis, as they do not have any other gene for that trait.
Inheritance restricted to males
Sex-restricted inheritance corresponds to genes located on the Y chromosome, called Holandric genes, which are inherited from the father and are present only in male offspring.
The Dutch gene SRY is responsible for the differentiation of testes in embryos from mammals.
The presence of thick, long hair on the ears is also a type of inheritance restricted to males, called hypertrichosis.
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Inheritance influenced by sex
Inheritance influenced by sex happens when genes are expressed in both sexes, however, they behave differently in men and women.
The baldness gene is influenced by sex, women can also have this characteristic, however, it is much more present among men.
This is because this gene is dominant in men and recessive in women, that is, for a woman to be bald, she must be homozygous recessive for this gene.
Sex Chromosome Related Diseases
color blindness
Color blindness is characterized by the individual's inability to distinguish red and green colors, occurring in 8% of men and only 0.04% in women.
This is because this is an X-linked inheritance, which is dominant in men and recessive in women, which implies that a woman will only be color-blind if both her parents are allele.
This is why there are many more men who are colorblind than women, as this trait only needs one allele to manifest in them.
Hemophilia
Hemophilia is an inherited condition in which the blood clotting system fails. People with hemophilia have severe bleeding even from superficial cuts.
As hemophilia is also X-linked, it is more common in men than women.
See too:
- Mind Map - Sexual Inheritance
- Inheritance
- Natural selection
- genetic drift
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