Construction and use of human chromosome jumping libraries from NotI-digested DNA

A basic difficulty in the molecular analysis of genes identified by mutations in the mammalian genome is the need to cover genetic distances corresponding to several hundred kilobases or more by molecular techniques like chromosome walking. In chromosome jumping, this limitation is overcome by the deletion of all but the extreme ends of large DNA molecules before cloning. We describe here the construction and characterization of a NotI 'jumping library' from human DNA. To characterize this library, random clones were analysed by restriction mapping. Clones carrying unique end fragments were characterized further by hybridization to Southern blots of NotI-cleaved human DNA separated on pulsed field gradient (PFG) gels. As a first step in a directional walk, the library was screened with a clone containing a NotI site cleaved in genomic DNA ('NotI linking clone') localized to the distal third of the short arm of human chromosome 4 (A.-M.F. & T.P., unpublished data). Starting and end points of two identified clones were positioned within a restriction map covering 850 kilobases.     

The pseudoautosomal boundary in man is defined by an Alu repeat sequence inserted on the Y chromosome

The Y chromosome, which in man determines the male sex, is composed of two functionally distinct regions. The pseudoautosomal region is shared between the X and Y chromosome and is probably required for the correct segregation of the sex chromosomes during male meiosis. The second region includes the sex-determining gene(s), the presence of which is necessary for the development of testes. The two regions have contrasting genetic properties: the pseudoautosomal region recombines between the X and Y chromosome; the Y-specific region must avoid recombination otherwise the chromosomal basis of sex-determination breaks down. The pseudoautosomal region is bounded at the distal end by the telomere and at the proximal end by X- and Y-specific DNA. We have found that the proximal boundary was formed by the insertion of an Alu sequence on the Y chromosome early in the primate lineage. Proximal to the Alu insertion there is a small region where similarity between the X and Y chromosomes is reduced and which is no longer subject to recombination.     

Über die Wirkung von 7,12-Dimethylbenz(a)-anthrazen auf die Synthese der Lactatdehydrogenase-Isoenzyme in menschlichen Fibroblasten

Summary The effect of 7,12-Dimethylbenz(a)anthracene (DMBA) on the activity of lactate dehydrogenase (LDH)-isoenzymes was studied in human fibroblast cultures. 3 isoenzyme components were separated by discelectrophoresis. A clear reduction in the enzymeactivity of the first and third component was observed, while the other fraction was little or not affected. The incorporation of radioactive amino acids in proteins of the LDH-isoenzyme bands shows the same trend.