Influence of the Parental Rhesus Types on the Segregation of Genetic Abnormalities

. Following the observation that in families with elliptocytosis parental Rhesus types may influence the elliptocytosis segregation in the children, the hypothesis has been put forward that in families with other genetic abnormalities, abnormal segregations of the affections may be expected to depend to some extent on the parental Rhesus types. Influence of the Rhesus type of the normal mating partners on the carrier: non‐carrier segregation in the children has been demonstrated for abnormal serum cholinesterase and for the chromosomal translocation D/21. Children of normal E+ mating partners in families with abnormal cholinesterase were found to have an excess of non‐affected; when the normal mating‐partner is E‐ there is an excess of carriers. In families with D/21 translocation an excess of carriers was found when the normal parent is E+. In a pedigree with Wagner's syndrome no such influence could be demonstrated, the amount of genetic information available being, however, relatively small. In families with the nail‐patella syndrome the Rhesus types of both parents appeared to be important, together with the sex of the offspring. Mating types involving Ccee produce an excess of non‐affected children, those with CCee an excess of affected sons and a deficiency of affected daughters. Mating types with neither Ccee or CCee produce a relative excess of affected daughters. These and other phenomena appear to indicate that genetic abnormalities are to some extent balanced polymorphisms, the selective mechanism being most probably selective fertilization. Selections of this kind, caused by the genetic, rather than by the external environment, may be of importance in limiting the increase of the genetic load in man which is generally expected to occur in the near future.