title: Linkage and genetic counselling for the fragile X using DNA probes 52A, F9, DX13, and ST14.
abstract: Linkage data using the markers DXS51, F9, DXS15, and DXS52 are presented from 14 pedigrees segregating with the fragile X. Cytogenetic and DNA data were combined by two- or three-point linkage analysis for estimation of lod scores and carrier probabilities in potential carriers. Recombination frequencies (theta) corresponding to maximum z scores (zeta) were obtained for DXS51 (zeta = 3.45, theta = 0.0), DXS15 (zeta = 0.40, theta = 0.06), F9 (zeta = 3.15, theta = 0.09), and DXS52 (zeta = 3.60, theta = 0.11) with the fragile X. Considerable alterations to carrier probabilities occurred in some cases, especially when flanking markers were informative. The chance of mentally impaired offspring was reduced to 1% for five of eight women with prior carrier probabilities of 32%. Three pedigrees were identified in which mutation had possibly occurred. An alternative explanation for two of these was inheritance of the fragile X from normal males and for the other inheritance from a clinically normal woman. Probabilities were computed for each of these alternatives.
mesh_terms: D004247:DNA / Q000032:analysis; D004274:DNA, Recombinant; D005600:Fragile X Syndrome / Q000175:diagnosis / Q000235:genetics*; D006580:Genetic Carrier Screening; D005817:Genetic Counseling; D005819:Genetic Markers; D006801:Humans; D008607:Intellectual Disability / Q000175:diagnosis / Q000235:genetics; D008126:Lod Score; D010375:Pedigree; D011110:Polymorphism, Genetic; D012150:Polymorphism, Restriction Fragment Length; D011995:Recombination, Genetic; D012306:Risk; D012729:Sex Chromosome Aberrations / Q000235:genetics*
chemical_list: D004274:DNA, Recombinant; D005819:Genetic Markers; D004247:DNA