Behavior of hobo and P transposons in yellow 2-717 unstable line of Drosophila melanogaster and its derivatives after crossing with a laboratory strain

Using fluorescent in situ hybridization technique (FISH), the frequency of hobo and P mobile elements transpositions on X chromosomes from the y ^2-717 , isolated from the Uman’ population of Drosophila melanogaster, as well as from its phenotypically normal and mutant derivatives, obtained as a result of crosses the males examined with the C(I)DX,ywf/Y females, was evaluated. It was demonstrated that the maximum frequency of hobo transpositions on X chromosomes of the males from derivative strains, subjected to repeated hobo-dysgenic crosses reached a value of 1.2 × 10^?2 per site per X chromosome per generation. The number of hobo copies in male X chromosomes from derivative strains was 3 times higher than in the original initial strain. Furthermore, the “old” hobo sites remained unchanged. In derivative strains, the frequency of hobo insertion was higher than that of excisions. One of the derivative strains, y ^1t-717a1k3-2 , was characterized by high intrastrain instability of hobo element localization. In the y ^2-717a1k3 and y ^1t-717a1k3-2 strains a large inversion, In(1)IB; 13CD, was described. At the absence of the full-sized P element in the strains involved in crosses, maximum frequency of P element transpositions in the derivative strains reached a value of 1.2 × 10^?2 per site per X chromosome per generation.     

Localization of single copy DNA sequences on G-banded human chromosomes by in situ hybridization

Recombinant lambda bacteriophage clone H3 containing a human DNA segment of 14.9 kb present in one or two copies per haploid genome was isolated. In situ hybridization to human metaphase chromosomes of the ³H-labeled cloned DNA resulted in highly significant labeling (53% of cells) of band p36 of chromosome 1, such that 22% of all chromosomal grains were located on this region. Hybridization was dependent upon the presence of dextran sulfate in the hybridization mixture and was not affected by repetitive DNA competitor. These results demonstrate localization of a single copy sequence on human metaphase chromosomes.     

DNA REPLICATION PATTERNS AND CHROMOSOMAL PROTEIN SYNTHESIS IN OPOSSUM LYMPHOCYTES IN VITRO

DNA replication patterns were determined in the autosomes and sex chromosomes of phytohemagglutinin-stimulated lymphocytes from the opossum (Didelphis virginiana) by employing thymidine-³H labeling and high-resolution radioautography. Opossum chromosomes are desirable experimental material due to their large size, low number (2n = 22), and morphologically distinct sex chromosomes. The autosomes in both sexes began DNA synthesis synchronously and terminated replication asynchronously. One female X chromosome synthesized DNA throughout most of the S phase. Its homologue, however, began replication approximately 3.5 hr later. The two X's terminated DNA synthesis synchronously, slightly later than the autosomes. This form of late replication, in which one X chromosome begins DNA synthesis later than its homologue but completes replication at the same time as its homologue, is apparently unique in the opossum. The male X synthesized DNA throughout S while the Y chromosome exhibited late-replicating characteristics. The two sex chromosomes completed synthesis synchronously, slightly later than the autosomes. Grain counts were performed on all chromosomes to analyze trends in labeling intensity at hourly intervals of S. By analyzing the percent of labeled mitotic figures on radioautographs at various intervals after introduction of arginine-³H, chromosomal protein synthesis was found not to be restricted to any portion of interphase but to increase throughout S and into G₂.     

CHROMOSOMAL BASIS OF DOSAGE COMPENSATION IN DROSOPHILA : III. Early Completion of Replication by the Polytene X-Chromosome in Male: Further Evidence and Its Implications

Thymidine-³H labeling patterns on the X (section 1 A to 12 E of Bridges' map) and 2 R (section 56 F to 60 F of Bridges' map) segments in the salivary gland chromosomes of Drosophila melanogaster have been analyzed in male and female separately. The observed patterns fit, with a few exceptions, in a continuous to discontinuous labeling sequence. In nuclei with similar labeling patterns on the 2R segment in both sexes, the number of labeled sites on the X in male is always less than in female X's. The labeling frequency of the different sites on the male X is considerably lower than those on the female X's, while the sites on the 2R segment have very similar frequency in the two sexes. The rate of thymidine-³H incorporation (as judged by visual grain counting) is relatively higher in male X than in female X's. It is concluded that the model sequence of replication in polytene chromosomes follows a continuous to discontinuous labeling sequence, and that the single X in male completes its replication earlier than either the autosomes in male or the X's in female. This asynchronous and faster rate of replication by the polytene X-chromosome in male substantiates the hypothesis of hyperactivity of the single X in male as the chromosomal basis of dosage compensation in Drosophila.     

The karyotypic variability of mouse embryonic fibroblasts of 2 genotypes during spontaneous neoplastic transformation

Karyological analysis of 6 lines with distinct tumorigenic properties of mouse strains C3H/He and C57BL/6 has been carried out using a differential staining of chromosomes. The number of normal copies of chromosomes varied in all the investigated cell lines. The more and the less stable chromosomes different from line to line. All the cell lines were characterized by decreased numbers of copies of normal chromosome 7; a decreased number of normal copies of chromosome 2 and 16 was detected in the course of the cell spontaneous neoplastic evolution. The decreased number of normal copies of chromosomes 8, 12 and X, and the increased number of normal copies of chromosome 10 were specific of the cell lines with intermediate tumorigenicity. The maximum tumorigenic cell lines differed from all other lines by increased numbers of copies of chromosomes 4 and 5, and by a decrease in copy number of chromosome 6. The data obtained are discussed in terms of the search of the regularity of karyotypic changes in the course of the cell neoplastic evolution.     

Relationship between the number and function of human ribosomal genes

Summary The relative number of ribosomal RNA genes of the acrocentric chromosomes in one individual was measured by counting grains after in situ hybridization of ³H-labeled human 18S rDNA to fixed metaphase chromosomes. The relative amount of ribosomal RNA gene activity of each of the same chromosomes was estimated by determining the frequency with which the chromosome's nucleolus organizer region (NOR) was silver stained, the size of the silver-stained region, and how often the chromosome was found in satellite association. Results were similar in phytohemagglutinin-stimulated T-lymphocytes, Epstein-Barr virus transformed lymphoblasts, and fibroblasts. One chromosome 21 had few gene copies and low activity. One chromosome 22 had many gene copies but low activity. Both chromosomes 14 had few gene copies but high activity. The level of expression that can be achieved by rRNA gene clusters can, therefore, be determined by factors other than the number of gene copies.     

Insect sex chromosomes

A presumptive mechanism of X inactivation has been investigated by using tritiated uridine-induced chromosome aberrations to distinguish active from inactive X chromosome arms in the insect Gryllotalpa fossor. Previous work on therian mammals has shown that constitutive and facultative heterochromatin are less susceptible to breakage by ³H-Urd than euchromatin (active). The present study indicates that, irrespective of the presence of two X chromosomes in females, only one of these is affected as in males and that the total number of aberrations induced by ³H-Urd in both male and female Gryllotalpa is the same. This suggests that in the female only one arm of one X chromosome is active and that a facultative heterochromatinization of the homologous arm of the other X is operative coupled with the presence of constitutive heterochromatin in the second arm of both X chromosomes.     

Localisation régionale des gènes humains IDHS,MDHS, PGK, α-GAL,G6PD par l'hybridation cellulaire interspécifique

Summary 22 independent man-hamster (HGPRT^–) hybrids using male human cells with balanced reciprocal translocation t(X;2)(p22;q32) were analysed for human genes localized on chromosome 2 (IDH_S, MDH_S), on chromosome X (PGK, GAL, G6PD) and for the different chromosomes in relation with the balanced reciprocal translocation (chr.2, chr.2q^–, chr.Xp⁺).The following results were obtained:The chromosomes 2 and 2q^– are absent in the 22 hybrids.In 9 hybrids, the absence of MDH_S in spite of the presence of the chromosome Xp⁺ indicates that the gene for MDH_S is not localized on this chromosome (or that the gene for MDH_S is not on the segment 2q32-2qter translocated on X).In 14 hybrids, the three markers of X (PGK, GAL, G6PD) and IDH_S are expressed in the presence of the chromosome Xp⁺. This result indicates that the genes for these markers are on Xp⁺ or that the genes PGK, GAL, G6PD are on X without the Xp22-Xter segment, translocated on the chr.2, and that the gene for IDH_S is on the 2q32-2qter segment translocated on X.In 8 hybrids, in the absence of the intact chromosome Xp⁺, the higher percentage of the presence of G6PD (7 hybrids) and the lower percentage of the presence of IDH_S (3 hybrids) are explained by the fact that these hybrids selected in HAT medium had to retain a segment of Xp⁺ bearing the human gene HGPRT. G6PD appeared very close to HGPRT and IDH_S very distant from HGPRT.The study of the different correlations between the presence and the absence of these four markers on Xp⁺ in the different hybrids indicates the following order on the chromosome Xp⁺ from p to q: IDH_s — PGK — GAL — G6PD.

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Groupe INSERM: Directeur J. Frézal

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Groupe CNRS, ER, 149: Directeur J. de Grouchy     

Induction and Transmission of a Merodiploid Condition near the Terminal Area of the Chromosome of BACILLUS SUBTILIS

A small fraction (about 0.5%) of the transformants for a particular marker of B. subtilis (ilvA4; most probably a deletion) were found to be relatively unstable merodiploids. They possess a redundancy of the metB–ilvA chromosome segment. When their DNA is used as donor in transformation a merodiploid condition for the whole of this segment is created in all ilvA4⁺ transformants. For several of the duplicated loci both copies often are of recipient strain origin. Markers originally belonging to different copies of the diploidized region can be contransferred in PBS1-mediated transduction. The data are well in agreement with the hypothesis that the merodiploids carry a tandem duplication. An alternative hypothesis which does not call for integration of the exogenote within the recipient chromosome was also considered. Models are proposed for interpreting the segregation of the merodiploids, the transmission of the diploid state and its generation during transformation of the ilvA4 marker by wild-type DNA.     

Meiotic mutations from natural populations ofDrosophila melanogaster

Two meiotic genes from natural populations are described. A female meiotic mutation,mei(1)g13, mapped to 17.4 on the X chromosome, causes nondisjunction of all homologs except for the fourth chromosomes. In addition, it reduces recombination by 10% in the homozygotes and causes 18% increased recombination in the heterozygotes. A male meiotic mutation,mei-1223 ^m144 , is located on the third chromosome. Although this mutation causes nondisjunction of all chromosomes, each chromosome pair exhibits a different nondisjunction frequency. Large variations in the sizes of the premature sperm heads observed in the homozygotes may reflect irregular meiotic pairing and the subsequent abnormal segregation, resulting in aneuploid chromosome complements.     

Genetic dissection of testis weight in mice: quantitative trait locus analysis using F2 intercrosses between strains with extreme testis weight, and association study using Y-consomic strains

In the present study, dissection of genetic bases of testis weight in mice was performed. Autosomes and the X chromosome were searched using traditional quantitative trait locus (QTL) scans, and the Y chromosome was searched by association studies of Y-consomic strains. QTL analysis was performed in ??DDD?×???CBA F₂ mice; the inbred mouse DDD has the heaviest testes, whereas the inbred mouse CBA has the lightest testes. Two significant testis weight QTLs were identified on chromosomes 1 and X. A DDD allele was associated with increased and decreased testis weight at the locus on chromosomes 1 and X, respectively. In the reciprocal cross ??CBA?×???DDD F₂ mice, QTL on chromosome 1, and not on chromosome X, had a significant effect on testis weight. The DDD allele at the X-linked locus could not sustain testis weight in combination with the Y chromosome of the CBA strain. The Y chromosome per se had a significant effect on testis weight, i.e., DH-Chr Y^DDD had significantly heavier testes than DH-Chr Y^CBA. On the basis of the results of Y-chromosome-wide association studies using 17 Y-consomic strains, variations in Uty, Usp9y, and Sry were significantly associated with testis weight. Thus, testis weight is a complex quantitative phenotype controlled by multiple genes on autosomes and sex chromosomes and their interactions.     

Karyotypes and X chromosome inactivation in segregants of a murine X-autosome translocation, T(X;4)37H

Karyotypes and X chromosome inactivation were studied in embryos obtained from female mice carrying T(X;4)37H translocation on day 6 to 8 of gestation by a BrdU-acridine orange method. A total of 18 different karyotypes were found in 477 embryos examined: 90.0% embryos were products expected from 2:2 alternate or adjacent 1 disjunction. 3:1 and adjacent 2 disjunctions accounted for approximately 8.0% and 0.7% conceptuses, respectively. In the embryo proper of balanced T37H/ + conceptuses, inactivation was random with respect to the normal X and the larger translocation X (4x) chromosome. In all the cells with the 4x inactive, the late replication apparently did not spread to the attached autosomal portion, although black/brown coat variegation implies spreading of inactivation into the autosomal region. The X chromosome segment deprived of the inactivation center remained active in all the cells examined and it exerted deleterious effects on embryonic or fetal development. Observation in embryos having two maternally derived X chromosomes showed that they were indeed resistant to inactivation in early extraembryonic cell lineages, and two copies of active X chromosomes in the trophectoderm fatally affected embryonic development due to inability to form the extraembryonic ectoderm and ectoplacental cone from the polar trophectoderm. In unbalanced X aneuploids the X chromosomes with the deletion were preferentially inactivated due to strong selection against nullisomy X.     

Transposition of the gene cluster CYC1-OSM1-RAD7 in yeast

A mutant of the yeast Saccharomyces cerevisiae contains an increased amount of iso-1-cytochrome c because two copies of a segment, denoted COR, were transposed to a new position on chromosome VII, while the original COR region was retained at the normal position on chromosome X; this COR segment encompasses the CYC1, OSM1 and RAD7 loci which determine, respectively, iso-1-cytochrome c, osmotic sensitivity and ultraviolet light sensitivity. The analysis of genomic DNA with cloned probes indicates that the length of the COR segment is approximately 12,000 base-pairs. We suggest that certain normal strains of yeast, which possibly may contain reiterated sequences, can produce extended transpositions similar to prokaryotes.     

黄鳝体内寄生胃瘤线虫的染色体核型及G-带分析

采用常规空气干燥法制片,对寄生于黄鳝(Monopterus albus)体腔内的胃瘤线虫(Eustrongylidesignotus)染色体核型进行分析。结果表明:胃瘤线虫体细胞有12条染色体,为二倍体,核型公式为2n=12=10 m+2 sm。由5对常染色体和1对性染色体组成,性别决定模式为XX-XY,其中X、Y和1～4号染色体都为中着丝粒染色体,5号为亚中着丝粒染色体。每对染色体都有特定的G-带带型。