Valerie Lindgren

Cytogenetic and molecular characterization of marker chromosomes in patients with mosaic 45,X karyotypes.

SummaryCytogenetic and molecular techniques were employed to determine the origin of marker chromosomes in five patients with mosaic 45,X karyotypes. The markers were shown to be derived from the X chromosome in three female patients and from the Y chromosome in one female and one male. One of the female patients, with a very small, X-derived ring chromosome, had additional phenotypic abnormalities not typically associated with Turner syndrome. In this patient, both the ring and the normal X chromosomes replicated early; perhaps the unusual phenotype is the result of both chromosomes remaining transcriptionally active. These studies illustrate the power of resolution and utility of combined cytogenetic and molecular approaches to some clinical cases.

Comparative analysis of mouse-human hybrids with rearranged chromosomes 1 by in situ hybridization and Southern blotting: high-resolution mapping of NRAS, NGFB, and AMY on human chromosome 1.

The human protooncogene NRASand the genes for the β-subunit of nerve growth factor (NGFB)and for amylase (AMY)have previously been assigned to the proximal short arm of chromosome 1, but their precise positions have not been unequivocally established. By in situ hybridization of DNA probes for the three genes, we have ascertained the location of complementary sequences in mouse-human somatic cell hybrids that contained translocations of chromosome 1. The results agreed with the presence or absence of the human sequences as determined by Southern blotting of hybrid cell DNA. The in situ data confirmed that the genes were present on the cytologically recognized rearranged chromosome. Compared to the autoradiographic silver grain distribution on normal human chromosome 1, our in situ results obtained with the translocation chromosomes allowed much greater precision of mapping. Both NRASand NGFBmap to band 1p22, and AMYwas confirmed in band 1p21.