Hereditary carrier

Autosomal dominant-recessive inheritance is made possible by the fact that the individuals of most species (including all higher animals and plants) have two alleles of most hereditary predispositions because the chromosomes in the cell nucleus are usually present in pairs (diploid).

According to Mendelian Law of Segregation of genes an average of 25% of the offspring become homozygous and express the recessive trait.

Examples of traits inherited via the X chromosome are color blindness and the most common hereditary form of haemophilia which therefore affect men much more often than women.

Both had children who continued to pass on the gene to succeeding generations of the royal houses of Spain and Russia, into which they married.

There are no carriers since owners of a dominant hereditary disposition phenotypically express the trait in each case.

Punnett square : If the other parent does not have the recessive genetic disposition, it does not appear in the phenotype of the children, but on the average 50% of them become carriers.
Punnett square: If both parents are carriers, on the average 25 % of the offspring have the recessive trait in phenotype and 50 % are carriers.
The mother is a carrier of the recessive hereditary disposition for Color blindness . The Y chromosome of the father cannot oppose this. The healthy allele on the X chromosome of the father can compensate for this in a daughter. She can see normally, but she becomes a conductor. The same pattern of inheritance applies to Haemophilia .
Inheritance by female carriers