Detection and Identification of Translocations by Increased Specific Nondisjunction in ASPERGILLUS NIDULANS

A meiotic technique for visual detection of translocations has been applied to ten mitotically identified interchanges, and three new translocations were discovered using this method. Testcrosses between "standard" strains and potential translocation strains-e.g. strains with newly induced mutants or descendants from translocation crosses-are inspected for the frequency of abnormal-looking colonies. In all heterozygous translocation crosses "abnormals" are increased at least tenfold compared to the average control level of 0.15%. Most of these are disomics, and can be recognized by their characteristic phenotypes. Each translocation produces a few specific types, since nondisjunction is increased mainly in the linkage groups involved in the translocation (50-100-fold over control values). Therefore, translocations were not only detected but often tentatively assigned to linkage groups from the analysis of the disomic progeny in crosses. In addition, this technique allows reciprocal and nonreciprocal translocations to be distinguished, since only the latter produce one-third phenotypically abnormal duplication progeny. While results are clearcut in most cases, occasionally problems are encountered, e.g. when morphological mutants segregate in crosses, or when other genetic factors which increase or reduce the frequency of nondisjunction are present in certain strains.     

The localization of a vitamin K-induced modification in an N-terminal fragment of human prothrombin

1. The N-terminal fragment (PF-I) split off from prothrombin during coagulation was purified to homogeneity from human serum. 2. The apparent molecular weight is 27000+/-2000 in sodium dodecyl sulphate-polyacrylamide-gel electrophoresis, whereas a value of about 19600 is obtained by calculation based on amino acid and carbohydrate analyses. The N-terminal sequence is an Ala-Asx bond. The fragment contains about 16% carbohydrate, binds phospholipids in the presence of Ca(2+) and is adsorbed to BaSO(4). The pK(a) of its BaSO(4)-binding group(s) is 3.1-3.5. 3. By CNBr cleavage of fragment PF-I two peptides (C-1 and C-2) were obtained with molecular weights of about 5900 (C-2) and 12400 (C-1) on the basis of amino acid and carbohydrate analyses. Only the smaller (N-terminal) peptide is adsorbed to BaSO(4) and, since the ability of the whole protein to bind to BaSO(4) is known to be absent in samples obtained from patients treated with vitamin K antagonists, this peptide probably contains the site of a modification to the structure of the protein which occurs during biosynthesis and depends on vitamin K. This peptide does not contain hexosamine or sialic acid.     

Nuclear function during early development of remote fish hybrids

The participation of paternal genome was studied in the development of remote hybrids obtained as a result of artificial insemination of the loach (Misgurnus fossilis) eggs by the sperm of aquarial Cyprinids (Brachydanio rerio, Danio malabaricus, Barbus tetrazona, Razbora heteromorpha, Carassius auratus) and Cobitids (Acanthophtalmus kuhlii). The hybrids obtained differed at the stage of hatching both from each other and from the loach by some morphological features. To study the function of heterologous nuclei, haploid nucleocytoplasmic hybrids were obtained by means of chromosome inactivation in the loach eggs by heavy doses of X-rays. The participation of paternal genome in development was estimated by comparison of the curves of viability of diploid and haploid hybrids with those of diploid, haploid and "anuclear" loach embryos. Patterns of mortality of embryos and larvae in each hybrid combination (percentage, stage) suggest the functioning of paternal genome already at the early stages of development. The activity of hybrid and heterologous nuclei was also estimated by the onset and the intensity of morphogenetic function which was determined by the time of embryonic death following nuclear inactivation at different stages. The onset of nuclear function in all hybrids coinsides with that in the loach, except B. rerio in which it occurs somewhat earlier. The data obtained prove the participation of paternal genes in development and maintenance of viability of embryos at all developmental stages beginning from the early ones (blastula).     

The fractionation of calf thymus DNA by multiple formation of sedimentable complexes with homologous lysine-rich histone KAP. Derivative melting curves and ultracentrifugation in CsCl concentration gradients

The process of fractionation of total calf thymus DNA using a step precipitation of DNA by means of increasing concentrations of the homologous histone KAP was investigated. In addition to the known fractions three so far undescribed ones/in thymus/,characterized by buoyant densities in CsCl equal 1.692, 1.706 and 1.728 g/ccm, were identified. Considerable amounts of preparations seriously enriched in individual satellite fractions were obtained. The ability of GC-rich satellite DNAs to form more soluble complexes with histone KAP is suggested as reason for the observed fractionation.