Transmission distortion: Distortion in the transmission of genes or chromosomes to the offspring, resulting in a significant difference from the Mendelian predictions. As a rule, the chance for a given gene or chromosome to be transmitted to a child is 1:1 or 50%. A number of biologic processes can distort this Mendelian prediction.
These processes include:
- meiotic drive which is preferential selection during meiosis (germ cell production);
- gametic selection which is preferential selection of gametes (germ cells) ; and
- postzygotic viability which reflects differences in the ability of conceptions to survive.
All of these mechanisms for selection result in the production of offspring in proportions that deviate from Mendelian predictions. For example, there may be a deficiency of offspring with an autosomal dominant syndrome due to the tendency for it to cause very early pregnancy loss. The proportion of offspring born with the syndrome is less than 50% due to selection.