Cytogenetic studies have shown that 40-60% of patients with Ullrich-Turner syndrome (UTS) are 45,X, whereas the rest have structural aberrations of the X chromosome or mosaicism with a second cell line containing a structurally normal or abnormal X or Y chromosome. However, molecular analysis has demonstrated a higher proportion of mosaicism, and studies in different populations have shown an extremely variable frequency of Y mosaicism of 0-61%. We used Southern blot analysis and polymerase chain reaction (PCR) to detect the presence of Ycen, ZFY, SRY, and Yqh in 50 Mexican patients with UTS and different karyotypes to determine the origin of marker chromosomes and the presence of Y sequences. Our results indicated the origin of the marker chromosome in 1 patient and detected the presence of Y sequences in 4 45,X patients. Taken together, we found a 12% incidence of Y sequences in individuals with UTS. The amount of Y-derived material was variable, making the correlation between phenotype and molecular data difficult. Only 1 patient had a gonadoblastoma. We discuss the presence of Y chromosomes or Y sequences in patients with UTS and compare our frequency with that previously reported.

SUMMARYThe relationship between the transfer systems of several plasmids was investigated, using as criteria complementation of a series of transfer-deficientFlacmutants, the efficiency of plating of F-specific phages, and identification of surface exclusion systems. The transfer systems of ColV2 and ColVBtrpwere similar to that of F except for surface exclusion: ColVBtrpspecified a surface exclusion system different from that of F, and ColV2 did not specify any detectable system. The transfer system of R1–19 was also similar to that of Flac, but the products oftraA,traIandtraJwere plasmid-specific. R1–19 determined the same surface exclusion system as ColVBtrp, and this was under the control of the transfer inhibitor. The transfer systems of ColIbdrdandFlacwere unrelated. ColEl was transferred byFlac traI−mutants, but not by mutants in other cistrons.

46,XX maleness is characterized by the presence of testicular development in subjects who lack a Y chromosome. The majority of affected persons have normal external genitalia, but 10–15% show various degrees of hypospadias. Several hypotheses have been proposed to explain the etiology of this constitution: translocation of the testis‐determining factor (TDF) from the Y to the X chromosome, mutation in an autosomal or X chromosomal gene which permits testicular determination in the absence of TDF, and undetected mosaicism with a Y‐bearing cell line. We report the pheno‐typic data and results of molecular analyses performed in six sporadic Mexican males with 46,XX karyotype. Molecular studies revealed Yp sequences in two individuals (ZFY+SRY+) with different phenotypes, a third one presented with a smaller segment of Yp (ZFY–SRY+) and complete virilization, while the remaining three were Y‐negative and showed hypospadias. In all subjects a hidden mosaicism with a Y‐bearing cell line was ruled out due to the absence of Y‐centromeric sequences. Our data demonstrate that the phenotype does not always correlate with the presence or absence of Y‐sequences in the genome, and confirm that 46,XX maleness is a genetically heterogeneous condition.

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