Because most of these are in somatic cells, they are not passed on to the next generation. It is also estimated that each human being is a carrier of around five recessive lethal genes. This happens when an affected male is infertile and the females do not express the disease. Then, the pedigree pattern will be identical to an X-linked recessive trait where males do not reproduce. Puberty praecox gene is only expressed in males.
Females transmit it to half of their sons.
The pedigree suggests a sex-linked inheritance. In autosomal recessive disorders, all children will be affected, 2. Both parents are healthy carriers of the mutation. If the gene has been shown to be segregating in previous generations with no diseased individuals, the penetrance may have been low in earlier generations. If it is an X-linked recessive disease and all the children so far are girls, the disease appears in the first male child.