ISSN:1424-8581    

DOI:10.1159/000132925

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The meiotic synaptic behavior of male mice heterozygous for one of two X-4 translocations was examined to test a recently advanced hypothesis (Ashley, 1988) suggesting that it is possible to predict the synaptic behavior (nonhomologous vs. homologous) and recombinational parameters (suppression vs. nonsuppression of crossing-over) of a chromosome aberration from mitotic G-band breakpoint data. The hypothesis was based on prior observations of synaptic behavior in a series of X-autosome translocations in mice. The breakpoints of the transloca tion T(X;4)7R1 are both in G-light bands. As predicted by the hypothesis, synapsis was restricted to homology. In contrast, one breakpoint of the translocation T(X;4)8R1 lies in a “stippled” band of the standard diagrams of Nesbitt and Francke (1981). As predicted (Ashley, 1988), “stippled” bands are shown here to synapse nonhomologously, i.e., they behave as “G-dark.” The linkage data, as they relate to the synaptic data and the predictions of the hypothesis, are als

ISSN:1424-8581    

DOI:10.1159/000132926

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The pachytene behavior of chromosomes participating in quadrivalent formation in male mice heterozygous for T(X;4)7R1 or T(X;4)8R1 was analyzed in electron micrographs of microspread spermatocytes. In each population of nuclei from the translocation heterozygotes, the longest 4X axes were approximately the proportional length expected from the respective contributions of the 4 and the X estimated from breakpoint positions in mitotic chromosomes. However, the 4X axis of these translocation quadrivalents undergoes extensive shortening. In both R7 and R8 the shortest 4X axis observed in the population of nuclei was approximately the length of the normal 4 axis. This equalization of axial lengths suggests that there may be an inter-chromosomal interaction between synapsed chromosomes. In R8, axial shortening of the 4X occurs as pachynema progresses. In both translocations, shortening is accompanied by twisting of the 4X around the 4. Both axial shortening and twists are characteristics exhibited by chromosomal axes of unequal length as part of the meiotic phenomenon described as “synaptic adjustment” (Moses, 1977). Synaptic adjustment involves, in addition, non-homologous synapsis, which is delayed until the latter part of pachynema. However, axial shortening in R7 and R8 is not accompanied by nonhomologous synapsis. In R7, nonhomologous synapsis does not occur; in R8, it is confined to quadrivalents in which the 4X axis is near its maximum length (i.e., early). This behavior suggests that axial shortening and nonhomologous synapsis during the progression of pachynema (previously considered collectively under the term “synaptic adjustment”) are not necessarily coupled

ISSN:1424-8581    

DOI:10.1159/000132927

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

Tetraploid mouse embryos were produced at the two-cell stage by blastomere fusion induced by inactivated Sendai virus. The embryos were from chromosomally normal female mice that had been fertilised by homozygous Rb( 1.3)1 Bnr males carrying a pair of large metacentric marker chromosomes in their karyotype. These “reconstructed” one-cell tetraploid embryos were then transferred to the oviducts of pseudopregnant recipients, which were subsequently autopsied early on the 10th day of gestation. Two-cell stage embryos that did not undergo blastomere fusion after 4–5 h were transferred to a second group of recipients, which were also autopsied early on the 10th day of gestation. From a total of 153 tetraploid embryos transferred to females that subsequently became pregnant, 135 implanted. Sixty-eight implantation sites were found to contain resorptions, whereas 67 contained mostly headfold presomite-stage embryos. Four embryos possessed four to six pairs of somites. All 57 em bryos that could be analysed cytogenetically were found to be tetraploid. G-banding analysis revealed that 30 of these embryos had an XXYY and 27 an XXXX sex-chromosome constitution. The presence of two marker chromosomes in all mitotic preparations from each of these tetraploid embryos confirmed that they had all been produced by duplication of their original XY or XX diploid chromosome constitution, respectively. The XXYY:XXXX sex ratio observed was not significantly different from unity. In the control series of transfers, all of the embryos recovered were at the forelimb bud stage and had a diploid chromosome constitution. The results reported here differ from human clinical findings, in which the XXYY:XXXX sex ratio of 120 human tetraploid spontaneous abortions recovered over the last 20 years is 45:75. Possible explanations for these differences are briefly disc

ISSN:1424-8581    

DOI:10.1159/000132928

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

A novel member of the SRC tyrosine kinase gene family was recently isolated and characterized (Hao et al., 1989). This FES/FPS-related gene, named FER, lacks the transmembrane and extracellular domains which characterize tyrosine kinases with receptor function. Expression of FER in a wide range of cell types indicates a general role in intracellular signalling or differentiation processes. We have now mapped FER to chromosome 5q14→q23 using in situ hybridization techniques and sug gest a more precise location within bands 5q21→q22. This region lies adjacent to a complex domain of growth factors and receptors, many involved in regulation of haematopoiesis. FER maps within a critical segment frequently deleted from chromosome 5 in patients with acute myeloid leukemia or myelodysplastic syndromes and was shown to be deleted in two such patients. It also maps close to the familial polyposis coli locus at 5

ISSN:1424-8581    

DOI:10.1159/000132929

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

A rapid method to identify sex in birds is described. The method requires microliter volumes of blood, and, under appropriate conditions, results can be available within an hour of sample collection. Samples can be stored at 4 C or–20 C with out sacrificing the ability to discriminate sex differences in DNA content. The assay will find utility in laboratory, field, and applied studies, in other classes of vertebrates, and in studies on the dynamics of genome size within and among population

ISSN:1424-8581    

DOI:10.1159/000132930

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

An interstitial deletion, 17cen→q11.2 (or q12), and a small extra chromosome was found in a sporadic case of von Recklinghausen neurofibromatosis (NFl). In situ hybridization with a chromosome 17-specific α-satellite probe showed that the small chromosome was derived from the deleted region, most likely by an exision/ring formation.—This chromosome rearrangement is in agreement with the localization of the von Recklinghausen neurofibromatosis (NF1) locus to the proximal region of 17q, but with a more distal breakpoint than observed in two previously described reciprocal translocations associated with NF1. If the NFl gene has been truncated by the present rearrangement, it may sug gest that the NF1 gene is a very large gene at the genomic level. Alternatively, NF1 in this patient may be caused by the gradual loss in somatic cells of the small chromosome carrying an intact NF1 gene, thereby suggesting a recessive mechanism at the gene level. Finally, an intact NF1 gene may have been placed in close proximity with α-satellite sequences, which might cause inactivation of the gene.—The small supernumerary chromosome may not only facilitate the cloning of the NF1 gene itself, but also offers explanations of the mechanism underlying development of the

ISSN:1424-8581    

DOI:10.1159/000132931

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

We have developed a technique of random primer extension of fixed chromosomes that is applicable to both mouse and man. Human chromosomes are not homogeneously labeled with this technique; those regions corresponding to R-bands appear to be more sensitive than those identified as G-bands, whereas centromeric regions are not labeled. These results not only cor roborate specific structural differences between distinct regions of mammalian genomes but also open up the possibility of assays with specific primers to test whether primer extension is useful for the identification of genes and families of sequences on chromosomes.

ISSN:1424-8581    

DOI:10.1159/000132932

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The karyotype of a triploid lemur hybrid, issued from the backcross of an Eulemur macaco male with a female E. coronatus hybrid is reported. The differential negative effect of the multivalents on male and female fertility is discussed.

ISSN:1424-8581    

DOI:10.1159/000132933

出版商:S. Karger AG    

年代:1990

数据来源: Karger

摘要:

The isolation and localization of a chromosome 12-specific α satellite DNA sequence, pα12H8, is described. This clone contains a complete copy of the 1.4-kb Hindlll higher-order repeat present within the α satellite array on chromosome 12. The specificity of pα12H8 was demonstrated by in situ hybridization and Southern blot analysis of a somatic cell hybrid mapping panel, both performed under high-stringency conditions. Polymorphic restriction patterns within the α satellite array, revealed by the use of the restriction enzymes Bglll and EcoRV, were demonstrated to display Mendelian inheritance. These properties make pα12H8 a valuable genetic marker for the centromeric region of chromoso

ISSN:1424-8581    

DOI:10.1159/000132934

出版商:S. Karger AG    

年代:1990

数据来源: Karger