| Citation | Distinguished for her outstanding contributions to human cytogenetics. As a member of the MRC Clinical and Population Cytogenetics Unit, she played a leading role in elucidating the chromosomal basis of abnormalities of sexual development, including the XXY Klinefelter karyotype, XXX women, XYY men, and the XY status of women with the androgen insensitivity syndrome (testicular feminization). By comparing the phenotypic effects of various Y chromosome abnormalities she inferred correctly that the "masculinizing" factor was located on the short arm of the human Y chromosome. By determining the incidence of structural rearrangements in a series of more than 10,000 unselected newborn infants, she was able to derive mutation rates, and in collaboration with Newton Morton to estimate the reproductive fitness of heterozygotes. In a later study of marker chromosomes in spontaneously aborted trisomic and triploid embryos, she succeeded in identifying the source of the extra chromosome or chromosome set. She was instrumental in devising the first method of karyotyping individual spermatozoa. Recently she has elucidated the androgenetic origin of a large series of hydatidiform moles, and has carried out extensive studies of the "fragile-X" chromosome. |