Genetics for the clinician / C.A. Clarke.

  • Clarke, Cyril A. (Cyril Astley)
Date:
1964
Catalogue details

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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    46 GENETICS FOR THE CLINICIAN one less than that in column 2, giving the diabetic offspring. This is because it is essential in each family to omit the propositus. If he were left in there would be an error in ascertainment, since the family would have been selected because it had an affected member in it. It is important to remember that in collecting sibships there is a tendency to discover those in which more than one member is affected (such families being far more notice¬ able) and a second or third sib may come back to the same hospital to be treated. The correct procedure is to start with a propositus, and having Table 3.3 16 in 72 — 22*2 per cent penetrance. once obtained him, to leave him out of the calculations and score only his sibs. If he were left in, the penetrance in this example would be raised from the correct figure of 22-2 to 48*6 per cent. However, if you ascertain the family by means of one of the parents then all the offspring can be utilized. The famiHes here were ascertained from the offspring. MULTIFACTORIAL INHERITANCE Here many genes, each with an additive effect, are concerned with the production of a character. The usual example, easy to comprehend, is that of height, this being a continuously variable trait and as such showing