摘要:

Karyotypic studies have been made of two species of South American snakes, Boa constrictor amarali and Bothrops jararaca. Both have 36 chromosomes; 16 macrochromosomes and 20 microchromosomes. While no morphological difference is discernible between the mitotic chromosome complements of the male and the female Boa constrictor amarali, a heteromorphic pair is evident in the female jararaca, in which the subterminal W is distinctly smaller than the mediocentric Z. Thus female heterogamety of the ZZ-ZW type is cytologically recognizable in Bothrops jararaca.

ISSN:1424-8581    

DOI:10.1159/000129740

出版商:S. Karger AG    

年代:1962

数据来源: Karger

摘要:

Karyological disturbances observed during the 6th to 17th subcultures in three lines of SV40-transformed human fetal renal cells were not evident in the 1st to 3rd subcultures of uninoculated control cells. The available evidence supports the hypothesis that the observed aberrations reflect changes in the cell genome attributable to cell-virus interaction at the time of transformation. An ancillary role of environmental factors during subcultivation subsequent to transformation in the selection of certain of the observed abnormalities is suggested by the experimental findings.

ISSN:1424-8581    

DOI:10.1159/000129742

出版商:S. Karger AG    

年代:1962

数据来源: Karger

摘要:

Karyotype analyses made from photomicrographs of 1303 human somatic cells derived mainly from peripheral leucocyte cultures obtained during the investigation of patients for chromosome aberrations, have been re-examined in order to determine the sites and relative frequencies of secondary constrictions. It has been confirmed that the chromosomes showing secondary constrictions most frequently in this material are chromosomes 13, 14, 15, 21 and 22. In these five pairs, a secondary constriction in the short arm separates a terminal mass, the satellite, from the rest of the chromosome arm. Secondary constrictions were also observed at specific sites in other chromosomes, although less frequently. In chromosomes 1, 6, 9 and 17 the constriction peculiar to each appeared in over 20% of the available chromosomes of the respective chromosome pair. Examples of secondary constrictions in these and other chromosomes are illustrated. Our observations provide evidence of at least fifteen sites, where constrictions are visible at a definite point with sufficient frequency to exclude any explanation other than that they are a distinct entity, characteristic for each chromosome. For each of these 15 constrictions, 10 chromosomes have been measured and the distance from the centromere to the constriction determined. The characteristic site of each constriction is indicated in a “normal human idiogram” constructed from chromosome measurements in 10 selected male cells. The value of secondary constrictions in the identification of human chromosomes is discussed, and the importance of recognising their location and variable appearance is stressed in view of the possibility that they may on occasions be interpreted as evidence of chromosome aberrat

ISSN:1424-8581    

DOI:10.1159/000129743

出版商:S. Karger AG    

年代:1962

数据来源: Karger

摘要:

1. In short-term tissue culture, bone marrow cells of adult chicken were treated with tritiated thymidine for the last 2–4 hours prior to fixation. Autoradiographs made from these cells permit the study of the final stages of DNA replication in the chromosomes. 2. Uptake of tritiated thymidine was found in both macro- and microchromosomes. Generally, the uptake ceases earlier in the microchromosomes than it does in segments of all six pairs of macrochromosomes. In the macrochromosomes, DNA synthesis is completed according to a distinct pattern. 3. In the homogametic male sex, the two Z-chromosomes were found to replicate DNA and to cease replication at a rate and time comparable to the other macrochromosomes. There is no significant difference in labeling pattern between the two Z’s. This is a remarkable contrast to the situation found in the homogametic female sex of the mammals. 4. In the heterogametic female birds, the single Z-chromosome showed a replication pattern not different in rate and relative timing from the two Z-chromosomes of the male. 5. In all of the labeled female cells and in none of the labeled male cells, a single element of the larger microchromosomes exhibited a very heavy and comparatively late uptake of tritiated thymidine. This observation is strongly reminiscent of the replication pattern of the mammalian Y-chromosome. It appears that this late labeling microchromosome is identical with the W-chromosome first reported by Frederic (19

ISSN:1424-8581    

DOI:10.1159/000129744

出版商:S. Karger AG    

年代:1962

数据来源: Karger

摘要:

Fourteen tests based on chromogenic enzymic reactions have been performed on clonal populations of a human embryonic epithelium cell strain (EUE) in order to determine which enzyme characters may best be studied for the detection and isolation of enzyme-deficient variants. The usefulness of the enzymic reactions in the selection of genetic markers was evaluated on the basis of the following considerations: a) sensitivity of the indicator reaction; b) effect on the viability of the cells; c) presence of spontaneous enzyme deficient variants. At present, two enzymes, namely, alkaline phosphatase and glucose-6-phosphate dehydrogenase, seem to be particularly suitable for study in the selection of variants bearing specific enzymic markers, and in fact, a number of deficient cell lines have been readily isolated from strain EUE.

ISSN:1424-8581    

DOI:10.1159/000129745

出版商:S. Karger AG    

年代:1962

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000129746

出版商:S. Karger AG    

年代:1962

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000129747

出版商:S. Karger AG    

年代:1962

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000129739

出版商:S. Karger AG    

年代:1962

数据来源: Karger