P. A. Jacobs

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In its expanded form, the fragile X triplet repeat at Xq27.3 gives rise to the most common form of inherited mental retardation, fragile X syndrome. This high population frequency persists despite strong selective pressure against mutation-bearing chromosomes. Males carrying the full mutation rarely reproduce and females heterozygous for the premutation(More)
To assess the possible association between aberrant recombination and XY chromosome nondisjunction, we compared pseudoautosomal region recombination rates in male meiosis resulting in 47,XXY offspring with those resulting in 46,XY and 46,XX offspring. Forty-one paternally derived 47,XXYs and their parents were tested at six polymorphic loci spanning the(More)
To assess the association between recombination and nondisjunction of chromosome 21, we analyzed cytogenetic and DNA markers in 104 trisomy 21 individuals and their parents. Our DNA marker studies of parental origin were informative in 100 cases, with the overwhelming majority (94) being maternal in origin. This value is significantly higher than the(More)
We measured muscle strength, joint motion, and gait parameters and determined the electromyographic activities of the ankle and knee during walking, running, and stair-climbing in two children who had had a tibial rotationplasty for osteosarcoma of the distal end of the femur. Both had marked loss of strength in the plantar flexors on the side of the(More)
Preliminary results on a large population-based molecular survey of FRAXA and FRAXE are reported. All boys with unexplained learning difficulties are eligible for inclusion in the study and data are presented on the first 1013 tested. Individuals were tested for the number of trinucleotide repeats at FRAXA and FRAXE and typed for four flanking(More)
There is an increased risk of leukemia in Down syndrome (DS) patients, with estimates ranging from 14 to 30 times the incidence rate observed for chromosomally normal children. Furthermore, one type of leukemia, called "transient leukemia" (TL), occurs almost exclusively in DS infants. The basis of the association between DS and leukemia is unknown, but we(More)
BACKGROUND In cultured, dividing transformed T lymphocytes and in dividing bone marrow cells from normal men and those with a haematological malignancy, sex chromosome aneuploidy has been found to increase in prevalence and degree with age. This has rarely been investigated in non-dividing uncultured blood samples. The loss and gain of the X chromosome in(More)
Reproductive outcomes and health of offspring were investigated in 340 patients with Hodgkin's disease first treated at Mount Vernon Hospital, Middlesex, England, at ages under 40 (females) or 45 (males) during 1970-91. Information on offspring was obtained from case-notes and postal questionnaires to the patients. Eleven men and 16 women who had conceived(More)