Social and genetic influences on life and death : a symposium held by the Eugenics Society in September 1966 / edited by the Lord Platt, A.S. Parkes.

Date:
[1967]
Catalogue details

Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: Social and genetic influences on life and death : a symposium held by the Eugenics Society in September 1966 / edited by the Lord Platt, A.S. Parkes. Source: Wellcome Collection.

    18/242 (page 4)
    4 INFLUENCES ON LIFE AND DEATH syndrome) just under three and a half months, and that of trisomy for number 18 (Edwards's syndrome) just over two and a half months.The rest of the autosome trisomies appear to be nearly always prenatally lethal. (2) By contrast, sex- chromosome trisomies would appear only seldom to cause prenatal death, and to cause far less serious abnormality in survivors than the autosome trisomies do. Further evidence of the greater tolerance of man to sex-chromosome imbalance is the fact that higher polysomy of the sex chromosomes has been found in survivors. Thus several males have been described with as many as four X chromosomes and a Y, and even a not very abnormal female with five X's has been detected, with a chromosome complement of 49. While trisomy, particularly of the sex chromosomes, but also of some of the autosomes, is compatible with survival at birth, the position as regards monosomy is very different. Monosomy is the absence of one chromosome from the proper diploid complement. The sex chromosomes are affected by the only fully monosomic condition, when, instead of being paired with an X or a Y, a single X chromosome is present, thus giving a chromosome complement of 45. Here again we have evi¬ dence of a considerable tolerance of man to sex-chromosome im¬ balance, but this is only relative, as there is ground for believing that this condition, the so-called XO state, is very often pre¬ natally fatal. In addition, many of the affected females sur¬ viving at birth are severely malformed, having what is named ' Turner's syndrome ', and practically all are sterile. Related to monosomy are chromosome deficiencies. Quite a rare one affects one of the autosomes of the group 4-5, the В group. It affects only one part of one member of a pair of chromosomes of this group, to be precise only the tip of the short arm of one member of the relevant chromosome pair. It produces a syn¬ drome of mental retardation with a distressing and cat-like cry in infancy known as the Cri-du-Chat syndrome.A second, and still rarer, type of deficiency, of which a dozen or so cases have been seen, involves the tip of one chromosome of pair number 18—another structural chromosome error with defi¬ ciency—and is often responsible for multiple somatic anomalies. The third type of deficiency has been described in a few