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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    THE CHROMOSOMES OF MAN 31 mongol because it has extra chromatin. If, however, a child inherits the translocation and also lacks a chromosome it will appear normal but be a carrier. This situation occurred in a large family of mongols described by Carter and his colleagues (i960) and the diagram (Fig. 2.5) is adapted from their paper. The division of mongols into those due to trisomy and those due to translocation is useful, yet both may occur in the same family. Thus two u о Û- -О о 15 I i) Arrows show where translocation will take place. 15 21 Q 2) Result of translocation. 21 ^21 4^ probably ■'/ /11 lost 3) (Below) Fl zygotes, receiving chromosomes from the affected parent above and also from an unaffected parent. 15 15 21 ? lethal I 1 15/ 15 /^1 It) 15 15 21 21 normal carrier Figure 2.5. Translocation in a mongol family. 21 21 mongol mongol sisters were found to have chromosome numbers of 46 and 47 respectively. The elder had the translocation product between a large and a small acrocentric autosome while the younger was trisomie either for chromosome 21 or 22. The mother and father both had normal counts of 46. Possible origins of the translocation are discussed in the paper (Barnicot et al, 1963). (2) in the 13-15 Group Here, in precisely the same way as a piece of chromosome 21 can be translocated on to 15, a piece of chromosome 13 can be translocated on to 15. Similarly, one would expect—and indeed it has been found—that when this occurs both translocation carriers and trisomies will result, the latter having the features shown on p. 29. A Liverpool family in which we