Antenatal diagnosis of genetic disease / edited by A.E.H. Emery.

Date:
1973
Catalogue details

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

Credit: Antenatal diagnosis of genetic disease / edited by A.E.H. Emery. Source: Wellcome Collection.

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    148 antenatal diagnosis of genetic disease age and other relevant variables for the particular family at risk. A series of risk tables have been prepared and a computer pro¬ gram (RISKMF) has been developed (Smith, 1972) to calculate the recurrence risk in any family presented. For example, the esti¬ mated recurrence risks for spina bifida and/or anencephaly are given in Table 23 for several different family histories. These methods are likely to be most useful; (1) in common familial conditions : (2) if there are sex or age effects; and (3) if there is a complex family history of the disease. It may be possible also to include information on correlated continuous traits associated with the disease, such as blood glucose in diabetes, to improve the accuracy of the risk estimate. Table 23. Estimated recurrence risks for spina bifida andjor anencephaly Family history of spina bifida Estimated recurrence Often the mode of inheritance is not known. Morton, Stevenson and Harris (1972) have developed a computer program (COUN¬ SEL) which will estimate risks for different modes of inheritance, including the multifactorial model, given information on incidence, ascertainment frequency, penetrance, family history and other relevant factors. Genetic Linkage and Antenatal Diagnosis The use of genetic linkage in genetic counselling and in ante¬ natal diagnosis has recently been discussed by Mayo (1970). In principle, if the disease locus is linked to a genetic marker, then information about the genotype of a fetus at the marker locus may give information about the genotype at the disease locus. As an example, consider use of the secretor locus (Se) in the diagnosis of myotonic dystrophy, the recombination fraction between these loci being about 0.07. An informative pedigree is given in Figure 23. To make a diagnosis, the linkage phase of the affected relatives