The measurement of linkage in heredity / by K. Mather.

  • Kenneth Mather
Date:
[1938]
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Licence: Attribution-NonCommercial 4.0 International (CC BY-NC 4.0)

Credit: The measurement of linkage in heredity / by K. Mather. Source: Wellcome Collection.

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    CHAPTER X HUMAN GENETICS (II) •26. LINKAGE THE question of linkage detection and estimation from human pedigrees is complicated by the same two difficulties, incomplete knowledge of the mating and small families, as is the consideration of single factor segregation. Where there is knowledge of three or more genera tions in the pedigree it is often possible to decide on the nature of the cross, and by lumping families from matings of the same type, to deal with the data by the methods adapted to the more usual types of genetical material. Ex. 19. For example, Halda'ne (1936) gives certain families segregating for retinitis pigmentosa, an eye defect. This anomaly is due to one of the so-called dominant genes, i.e. the heterozygote is the type usually distinguished from the normal. The problem at issue was that of whether the gene for retinitis pigmentosa was incompletely linked to sex or not. The informative families are those from the mating of affected men and normal women. The male parent is then heterozygous for both sex and the eye defect. It is, however, also necessary to know the phase of the linkage, whether coupling or repulsion. With a dominant gene such information is usually easy to obtain. These retinitis pigmentosa pedigrees give the required information in telling whether the man in question received the defect from his father 110