Genetics for the clinician / C.A. Clarke.

  • Clarke, Cyril A. (Cyril Astley)
Date:
1964
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Licence: Attribution-NonCommercial-NoDerivatives 4.0 International (CC BY-NC-ND 4.0)

Credit: Genetics for the clinician / C.A. Clarke. Source: Wellcome Collection.

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    84 GENETICS FOR THE CLINICIAN total incidence of these was not raised yet there were some very unusual findings in. particular cases, certain abnormalities having declined in fre¬ quency and others increased—and these changes were apparently depend¬ ent on the race of the father. Since there is no known genetic mechanism, except for Y linkage, which operates primarily through the father Morton felt that these changes must be environmental. Haldane (1922) has shown that where there is an upset of the sex ratio in race crosses in animals it is usually in the direction of a deficiency of the heterogametic sex (see glossary for explanation of Haldane's rule). The rule is particularly well exemphfied in race crosses in the Lepidoptera where there are often large excesses of males (XX), and if the same thing were to happen in Man the excess would be of females. Investigation of sex ratios in Man is beset with difficulties but there is a hint that there may I ¿íi ¿Vo Ею i 8 9 ¿ ¿ ¿ E]'¿ ¿ ¿ I 2 3 4 5 б 7 8 9 10 II 12 13 H CHINESE m CAUCASIAN Д 5: D. aet 25. Ca. Rectum. П^: D.aet 2, ТВ.Meningitis. Ш9: D.aet 2,Acute Leukaemia. Pedigree 7. i be an excess of women in a population of F.i. hybrids (Negro X Cauca¬ sian) studied by Miller and Harrison (personal communication). However, if the trend noted is a true bill it is surprising that it has not been reported before. Apart from the sex ratio it is possible that there could be in race crosses in Man some genie imbalance since different translocations might have been selected for in different races. Such imbalance might conceivably predispose to certain diseases and cancer is one that particularly comes to mind. It may be nothing more than a coincidence that in Pedigree 7. i the propositus died of carcinoma of the rectum at the age of 24 years and