ISSN:1424-8581    

DOI:10.1159/000131560

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

A series of marsupial-eutherian somatic cell hybrids was produced by fusion between lymphocytes from the red kangaroo (Macropus rufus) and HPRT-deficient mouse cells. The hybrids lost marsupial chromosomes and could therefore be used to map marsupial genes. Several of the hybrids contained a complete red kangaroo X chromosome and expressed the kangaroo form of the enzymes HPRT, G6PD, and PGKA. A number of HPRT-deficient revertant cell lines were derived from the hybrids. These possessed a variety of partially deleted X chromosomes. With these cell lines, it has been possible to establish the X-linkage of the genes for HPRT, G6PD, and PGKA in this marsupial and to localize these three genes to the terminal portion of the euchromatic arm of the red kangaroo X chromosome.

ISSN:1424-8581    

DOI:10.1159/000131561

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

The present paper describes three cases of heteromorphic sex chromosomes in fishes of the genus Leporinus (Anostomidae). An XX/XY type was found in Leporinus lacustris and a ZZ/ZW type in L. silvestrii and L. obtusidens. These facts agree with the observations of Ebeling and Chen (1970), who suggested that heterogamety evolved not once but many times among the teleosts.

ISSN:1424-8581    

DOI:10.1159/000131562

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

A lymphoblastic leukemia cell line, L5178YR, that is over 100,000-fold resistant to methotrexate (MTX) has been developed. Previous work has demonstrated that the resistant line has dihydrofolate reductase (DHFR) levels 300-fold higher than the sensitive parental cells, L5178Y. Resistant cells grown in the absence of MTX (L5178YR–) showed a similar level of DHFR activity. The increase in DHFR could be entirely accounted for by a corresponding increase in DHFR-specific mRNA and gene copies. Studies were carried out to determine whether these changes in the resistant cells were accompanied by karyotypic alterations. A detailed karyotypic analysis of the sensitive parental line (L5178YS) and the two resistant cell lines (L5178YR+ and L5178YR-) was performed. Although certain abnormal marker chromosomes were present in all three cell lines, the most striking consistent difference between the resistant and sensitive cells was the presence of a large, faintly banded region of intermediate staining intensity, termed a “homogeneously staining region” (HSR), inserted within a reduplicated part of chromosome 2. It was present in approximately 90% of resistant cells, and no more than one HSR was ever present in a cell. Hybridization in situ was performed to determine the chromosomal locations of DHFR genes. Utilizing a purified complementary DNA probe made from messenger RNA of the L5178YR+ cells, the genes were shown to be localized exclusively to th

ISSN:1424-8581    

DOI:10.1159/000131563

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Comparative studies of the number of cellular chromosomes and viral genes, including the gene required for malignant transformation, were performed on several clones of Rous sarcoma virus-transformed, revertant, and spontaneously retransformed field vole cells. The results of these studies indicate that no appreciable differences in either total viral gene equivalents or transforming gene sequences can be detected between transformed and revertant cell types, even though considerable differences in the number of certain chromosomes exist among the clones tested. Furthermore, no increase in the amount of total genes or transforming gene sequences accompanies retransformation of revertant clones, including clones that exhibited significant increases in chromosome number following retransformation.

ISSN:1424-8581    

DOI:10.1159/000131564

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

In the hybrids between Japanese wild mice (Mus musculus molossinus) and inbred laboratory mice (BALB/c and B10.BR, which were probably derived from M. m. domesticus), the X and Y chromosomes dissociated precociously at the first meiotic metaphase in some 70% of spermatocytes; that percentage was only 8.9% in inbred laboratory mice and 21.1% in wild mice. X-Y dissociation began at least at early diakinesis and continued during metaphase I (MI). Some autosomes of the hybrid (10.1%) and BALB/c (10.6%) mice also dissociated precociously, but there was no distinctive correlation between X-Y and autosomal dissociation. In BIO or B6 congenic lines with a Y chromosome from wild M. m. molossinus, there was an apparent tendency for the percentage of precocious X-Y dissociation to decrease with an increasing number of back cross generations. Based on these observations we concluded that: 1. the X-Y dissociation found is genetically controlled, perhaps by multiple genes; 2. these genes are located on autosomes and are active only when they are heterozygous; 3. the frequent dissociation of the sex chromosomes neither affects male fertility nor induces non-disjunction of the X and Y chromosomes, though it significantly reduces testes weight.

ISSN:1424-8581    

DOI:10.1159/000131565

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

A preferential loss of rabbit chromosomes was observed in 20 independent rabbit/hamster hybrid clones. Sixteen of these clones were analyzed for the enzymatic markers known to be X-linked in many species: HPRT, G6PD, PGK, GLA. These markers were shown to be syntenic, and the genes coding for them were localized on the rabbit X chromosome.

ISSN:1424-8581    

DOI:10.1159/000131566

出版商:S. Karger AG    

年代:1981

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000131567

出版商:S. Karger AG    

年代:1981

数据来源: Karger