摘要:

In heterozygous carriers of the mouse reciprocal translocation T(14;15)6Ca, the frequency of nondisjunction involving the minute marker chromosome was 4.4 % in the male and 22.2 % in the female. The fate of gametes with unbalanced genomes derived from normal as well as abnormal meiotic disjunction in T6 heterozygotes was investigated on the basis of chromosome counts at metaphase II and karyotype analyses in early postimplantation embryos produced by backcrossing with chromosomally normal animals. Results obtained indicate that meiotic, gametic, and zygotic selection attributable to specific types of chromosomal imbalances is minimal, if any, by the late blastocyst stage. All zygotes with unbalanced genomes, except those with 20 normal pairs plus the minute marker, however, die off in the latter half of pregnancy. Therefore, the increased incidence of translocation trisomics among progeny of female as compared with male heterozygotes reflects the higher incidence of nondisjunction in primary oocytes than in spermatocytes.

ISSN:1424-8581    

DOI:10.1159/000130494

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

A new fluorescence plus Giemsa staining technique now makes the detection of sister-chromatid exchange (SCE) a relatively easy matter in cells containing 5-BrdU-substituted DNA. The technique has been applied to human cells to examine the distribution of SCE between different people and between and within different chromosomes. The results show: (1) That there were no large differences in the incidence of SCE between blood leukocyte chromosomes from male and female adults and newborn, and that similar frequencies were found in cells from two patients with ataxia telangiectasia which, nevertheless, showed the typical increases in chromosomal aberrations. (2) The distribution of SCE between chromosomes in the complement was found to be proportional to chromosome length, although the smaller chromosomes were under-represented, but not significantly so. (3) The distribution of SCE within chromosomes was nonrandom, with a deficiency in the centromeric and an excess in the mid-arm regions. There was no evidence for an excess of SCE in chromosome regions rich in AT DNA sequences. (4) The frequency of SCE is to some extent dependent on 5-BrdU concentration, but the influence of concentration is minimal within the range of from 1 to 160 µm. Human cells exposed over two cell cycles at these higher BrdU levels have around 14 SCE per cell–a frequency virtually identical with that observed in cultured cells from the Chinese hamster, wallaby, and rat kangar

ISSN:1424-8581    

DOI:10.1159/000130495

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

A mutant cell bank in support of research in aging has been established at the Institute for Medical Research, Camden, N.J. The bank is under contract support of the Adult Development and Aging Program of the National Institute of Child Health and Human Development. We anticipate that the bank, with associated services such as an annual workshop, will facilitate the growth of the NIH grant-supported cellular aging research program and thus contribute to the elucidation of mechanisms in human aging at the cellular and molecular level.

ISSN:1424-8581    

DOI:10.1159/000130496

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

Translocations involving entire chromosomes or whole chromosome arms may not necessarily require deletion of a centromere. Conceivably, in the process of centromeric or telomeric fusion or of fusion of a centromere with a telomere, centromeric inactivation may occur, thus preserving both centromeres—one functional, the other latent—in the resultant translocation chromosome. If such latent centromeres exist and, in addition, are capable of being reactivated, it would explain how additional functional centromeres are acquired in the reverse process of chromosomal fission or fragmentation. A system of nomenclature is proposed for identifying the origin and nature of these chromosomal rearrangeme

ISSN:1424-8581    

DOI:10.1159/000130497

出版商:S. Karger AG    

年代:1975

数据来源: Karger

摘要:

The major site of genes for human 5S RNA is in the long arm of chromosome 1. We find no evidence of sites in other chromosomes; if such exist, they are much smaller than the site in 1q.

ISSN:1424-8581    

DOI:10.1159/000130498

出版商:S. Karger AG    

年代:1975

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130499

出版商:S. Karger AG    

年代:1975

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130500

出版商:S. Karger AG    

年代:1975

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130501

出版商:S. Karger AG    

年代:1975

数据来源: Karger