摘要:

Segregation after mitotic crossing-over in an isodicentric (idic) X chromosome with one active and one inactive centromere has given rise to two new cell lines, one in which the idic(Xpter) chromosome has two active centromeres (most of these chromosomes also have an inversion) and another in which neither centromere is active. The two X chromosomes are attached at the telomeres of their short arms. Similar segregation has given rise to two other cell lines with idic(Xq-) chromosomes. Other observations on segregation after mitotic crossing-over are reviewed. Unequal crossing-over has apparently played a major role in the evolution of various genes and heterochromatin. Retinoblastoma and Wilms tumor are in some cases associated with homozygosity of a chromosome segment resulting from mitotic crossing-over. Similarly, the high incidence of cancer in Bloom syndrome may be caused by mitotic crossing-over leading to homozygosity or amplification of oncogenes.

ISSN:1424-8581    

DOI:10.1159/000132453

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Mitotic analyses of the brook trout (Salvelinus fontinalis) × arctic char (S. alpinus) hybrids (sparctic trout) revealed a mode of 2n = 82 with 18 metacentric and 64 acrocentric chromosomes. The brook trout had 2n = 84 with 16 metacentric chromosomes and the arctic char had 2n = 80 with 20 metacentric chromosomes; both species are derivatives of a single tetraploid event. Variable multivalent-like configurations that may be centromeric associations of bivalents were observed in C-banded pachytene figures of female sparctic trout. Metaphase I analyses of sparctic trout males indicated that two fusions of nonhomologous acrocentric chromosomes representing two duplicated chromosome sets must have occurred in the arctic char after its evolutionary divergence from the brook trout. A mode of seven tetravalent rods per cell suggests that preferential multivalent pairing occurs in the sparctic hybrid; metaphase I analyses of S. alpinus males revealed a mode of only five tetravalent rods per cell. The presence of multivalents implies that the arctic char, like the brook trout, is still undergoing diploidization. Cytochemical detection of the nucleolar organizer region (NOR) revealed intra- and interspecific as well as intraindividual variability in the numbers and types of chromosomes (metacentric or acrocentric) on which NORs appeared in arctic char and sparctic trout. Brook trout only had NORs on acrocentric chromosomes. This may indicate that different chromosomal fusions occurred in the evolution of brook trout from arctic char

ISSN:1424-8581    

DOI:10.1159/000132454

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Trypsin G-banded karyotypes of eight species of Ursidae were prepared from retrovirus-transformed skin fibroblast cultures. The banding patterns of all bears are highly conserved, even though their diploid numbers range from 42 to 72. A comprehensive analysis of the homologous banding patterns within the Ursidae and with a hypothesized ancestral carnivore karyotype permitted the reconstruction of three significant chromosomal reorganization events that occurred during the evolution of the modern ursids. The first was a multichromosomal fissioning away from the biarmed (2n = 44) primitive carnivore karyotype, leading to six species of the Ursinae subfamily (2n = 78). The second was a comprehensive chromosome fusion in the lineage that led to the Ailuropodinae (giant panda) subfamily (2n = 44). The third event was a second, independent, but less extensive, centromeric fusion occurring in the line that led to the Tremarctinae (spectacled bear) subfamily (2n = 52). Ursidae karyotypes are not only highly conserved within the family but also exhibit extensive chromosome banding homology with other carnivore families.

ISSN:1424-8581    

DOI:10.1159/000132455

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

An uncultured immunoblastic lymphoma, obtained from an untreated patient, was examined from a cytogenetic, immunophenotypic, and molecular viewpoint. The B-cell lineage, immunoglobulin light-chain type, and percentage of neoplastic cells were determined immunologically. Karyotyping showed the presence of a 14q+ marker and suggested that the donor chromosome was chromosome 8. Southern-blot analysis of DNA from normal and lymphoma cells, using as molecular probes sequences related to the IGHJ and IGK immunoglobulin genes, confirmed the immunophenotype. A similar analysis, using probes homologous to IGHAC and MYC genes, showed that the t(8;14) detected by cytogenetic analysis resulted in a IGHAC-MYC rearrangement.

ISSN:1424-8581    

DOI:10.1159/000132456

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

Chicken chromosomes were identified up to No. 18 by a sequential counterstain-enhanced fluorescence technique. A heterochromatin characterization of macro- and microchromosomes was performed; in general, the microchromosomes were GC-rich, but with a high degree of variation. The NORs are localized on chromosome No. 17.

ISSN:1424-8581    

DOI:10.1159/000132457

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

One sterile and one subfertile man with balanced reciprocal autosomal translocations, a t(9;15), and a t(14;21), were analyzed using whole mount pachytene spreads, histology, and semen analyses. In both probands with different types of quadrivalent complexes lack of pairing near the translocation breakpoints and significant associations with XY bivalents were found. Variability in the frequency of XY-quadrivalent contacts and an increase in late pachytene to 52% in t(9;15) and 90% in t(14;21) could be observed. The lower rate was associated with reduced postmeiotic spermatogenesis and the higher rate with complete spermatogenic arrest. In both translocation carriers the XY-quadrivalent association is considered to be the main cause for testicular malfunction rather than nonpaired segments in the multivalent complexes.

ISSN:1424-8581    

DOI:10.1159/000132458

出版商:S. Karger AG    

年代:1987

数据来源: Karger

摘要:

The gene for renin, previously mapped to human chromosome 1, was further localized to 1q12→qter using human-mouse somatic cell hybrid DNAs. The renin DNA probe used (λHR5) could detect a HindIII restriction fragment length polymorphism. When used in studies of 12 informative families, no linkage could be found between the renin gene and Charcot-Marie-Tooth disease. Furthermore, an association of any renin allele with hypertension was not appare

ISSN:1424-8581    

DOI:10.1159/000132459

出版商:S. Karger AG    

年代:1987

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000132460

出版商:S. Karger AG    

年代:1987

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000132461

出版商:S. Karger AG    

年代:1987

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000132466

出版商:S. Karger AG    

年代:1987

数据来源: Karger