Dominant transmission related to X

A Genetic disease is known as of dominant transmission related to X when

  • the abnormal Gène is on the sexual Chromosome X.
  • the presence of only one abnormal Gène is sufficient so that the Maladie is expressed at a boy
  • the presence of only one abnormal Gène is sufficient so that the Maladie is expressed at a fille.
The abnormal Gène is transmitted either by the father or by the mère.
  • If the gene is transmitted by the father, this one is obligatorily sick
  • If the gene is transmitted by the mother, this one is obligatorily sick also because the abnormal gene is dominant
During the gamétogenèse, the male or female cells pass from 2n Chromosome S (cell Diploïde) to N Chromosome (cell Haploïde). The abnormal gene is thus present in half of the Gamète s.
The characteristics of a genetic disease with dominant transmission related to X are the following ones:
  • It reaches the men as much as the women.
  • the father does not transmit his disease to its boy (except if his wife is carrying gene).
  • the mother transmits her disease to her daughters.
But to be carrying gene inevitably does not mean to be sick, the demonstrations of a genetic disease depend on its Pénétrance and the Variabilité of its expression

General outline of the dominant transmission related to X

In the diagrams, the gamètes carrying normal gene are in blue, the gamètes carrying abnormal gene are in red. The sick people are in red, the nonsick people but carrying gene are purple, the people noncarrying gene are in blue.

Union of a sick man and a noncarrying healthy woman

Like this diagram shows it:
  • No boy will be reached since Y is obligatorily transmitted to them.
  • All the girls will be malades

Union of a healthy man and a sick woman

Like this diagram shows it, this couple has, with each pregnancy, a risk:
  • 1/2 to have a boy carrying abnormal gene thus sick
  • 1/2 to have a boy noncarrying abnormal gene thus healthy
  • 1/2 to have a girl carrying abnormal gene thus sick
  • 1/2 to have a girl noncarrying abnormal gene thus healthy

Union of a sick man and a sick woman

Like this diagram shows it, this couple has, with each pregnancy, a risk:
  • 1/2 to have a boy carrying abnormal gene thus sick
  • 1/2 to have a boy noncarrying abnormal gene thus healthy
  • 1/2 to have a carrying girl homozygote thus sick
  • 1/2 to have a carrying girl hétérozygote thus sick

General base of the the genetic Council in the dominant diseases related to X

In genetics, the proposer nominates the person reached of the genetic disease from which one makes the genetic Conseil.

Relative of a proposer

Phratry of a proposer

Descent of a proposer

Sources

See too

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