摘要:

An attempt was made to confirm the linear dose-effect kinetics reported by H. J. Evans for the production of two-break aberrations in X-irradiated human leukocyte cultures fixed after 52 to 56 h incubation. Although Evans’ experiments were carefully duplicated, the yield of two-break aberrations showed the same essentially dose-square kinetics observed at all fixation times by other workers using different culture methods. Thus Evans’ suggestion that culture technique influences dose-effect kinetics was not confir

ISSN:1424-8581    

DOI:10.1159/000130036

出版商:S. Karger AG    

年代:1969

数据来源: Karger

摘要:

The karyotypes of 15 species of snakes are described: Lachesis muta noctivaga, Micrurus lemniscatus carvalhoi, Philodryas aestivus aestivus, P. patagoniensis, P. serra, Thamnodynastes pallidus nattereri, T. strigatus, Tomodon dorsatus, Xenodon neuiviedii, Liophis miliaris, Erythrolamprus aesculapii venustissimus, Hydrodynastes bicinctus schultzi, H. gigas, Pseustes sulphureus sulphureus and Oxyrhopus petolarius. The diploid number varied from 24 to 46 between species of the family Colubridae. During evolution, variation of the chromosome number in the suborder Serpentes occurred mostly by rearrangements of genetic material rather than by alterations of the DNA amount. Different stages of heteromorphic sex-chromosome differentiation were detected in the species analyzed; these ranged from absence of heteromorphism in either sex to striking differences in form and size of the sex heterochromosomes in the female.

ISSN:1424-8581    

DOI:10.1159/000130037

出版商:S. Karger AG    

年代:1969

数据来源: Karger

摘要:

The Y chromosome of the Chinese hamster is late replicating in spermatogonial mitoses labelled in vivo. During the last two hours of the S phase the long arm of the Y replicates the majority of its DNA. The short arm terminates replication before this. Replication of the long arm of the X takes place earlier in S, whereas the short arm of the X is synchronous with that of the Y. Two small metacentric autosomes are also late replicating, in synchrony with the long arm of the Y. The distinct pattern of late replication of the Y chromosome of spermatogonia is in agreement with our experience with other mammals. The replication patterns of spermatogonia and a morphological study of the XY bivalent in primary spermatocytes indicate that the X and Y chromosomes pair by their short arms.

ISSN:1424-8581    

DOI:10.1159/000130038

出版商:S. Karger AG    

年代:1969

数据来源: Karger

摘要:

A statistical study of early and late DNA synthesis in segments of chromosomes from XXY fibroblasts was performed in order to establish the accuracy of karyotyping on a morphological basis in relation to the labelling patterns over the chromosomes. Cells were labelled with 3H-thymidine after incomplete synchronisation with a DNA inhibitor (5-fluorodeoxyuridine). The late-S pattern was, in general, found to complement the early-S pattern, and 71 % of the chromosome segments were significantly either early or late labelling. The larger late-labelling segments, typified by those in chromosome 4 and the late-labelling X, continue synthesis after the smaller ones (Nos. 21 and 22 and the Y) have more or less reached completion. In 40 cells from late- or early-labelled samples, where chromosomes were first karyotyped without reference to labelling behaviour, the following chromosomes showed significantly distinct patterns and could be distinguished from each other or from other chromosomes in their Denver groups: Nos. 4 and 5, the early-labelling X, Nos. 9, 11, 13, 17 and 18 and the Y. In a sample of 20 cells labelled at an early or penultimate stage of late-S, other chromosomes, including Nos. 14, 15, 21 and 22, showed unique labelling patterns. At no stage could chromosomes 8 and 10 or 19 and 20 be distinguished from one another in their respective groups on the basis of labelling pattern. The study indicates that even with errors arising from misclassification of chromosomes and the inherent within- and between-cell variability in labelling, significant differences in labelling behaviour of chromosomes can be demonstrated in a partially synchronised population labelled at the correct stage of DNA synthesis.

ISSN:1424-8581    

DOI:10.1159/000130039

出版商:S. Karger AG    

年代:1969

数据来源: Karger

摘要:

DNA replication studies were carried out on metaphase plates showing satellite associations to determine the association of individual D chromosomes. In a total of 279 D chromosomes involved in satellite associations and identified by autoradiography, it was found that the association of the three members of the D chromosomes was random. In D/D associations no prevalence of homologous combination was observed. In addition, a case of D trisomy and three cases with t(GqDq) (from two unrelated families) were studied. The extra D chromosome in the first case was identified as a No. 13 by the labelling pattern. In the other three cases, the D chromosome involved in the translocation was identified as a No. 14. Studies of satellite associations in these cases are also described.

ISSN:1424-8581    

DOI:10.1159/000130040

出版商:S. Karger AG    

年代:1969

数据来源: Karger

摘要:

We studied the influence of the method used in cultivating and preparing lymphocyte cultures on the quantitative and qualitative association patterns of the acrocentric chromosomes in the same individual. We compared the results obtained by macrocultures with medium TC 199 (method a), by macrocultures with McCoy’s medium 5A (method b) and by microcultures with McCoy’s medium 5A and 20% fetal calf serum (method c). These comparisons were made under two conditions: (1) fixation with glacial acetic acid/methanol 1:3 and (2) subsequent resuspension in 70% acetic acid. For cultures that were not resuspended, no marked differences could be observed in the quantitative association types {i.e., the number of associating chromosomes). As regards the qualitative association types (i.e., the relative frequency of participation of D and G chromosomes), however, an increasing deviation from the expected D-D:D-G:G-G ratio from method a to b to c, caused by an increase in G-G associations, could be demonstrated. In cultures resuspended in 70% acetic acid subsequent to the usual fixation process a significant increase in associations (primarily in associating G chromosomes) could be observed for all methods. Mechanical factors possibly responsible for these results are discus

ISSN:1424-8581    

DOI:10.1159/000130041

出版商:S. Karger AG    

年代:1969

数据来源: Karger

摘要:

An apparently identical balanced translocation (3?–;G?q+) was observed in two unrelated families. The translocation in both kinships was ascertained through a propositus who had trisomy G Down’s syndrome in addition to the balanced translocation. Although the occurrence of these chromosome abnormalities in the same individuals could have been coincidental, other possible explanations were conside

ISSN:1424-8581    

DOI:10.1159/000130042

出版商:S. Karger AG    

年代:1969

数据来源: Karger

摘要:

A sterile phenotypically male mouse proved on dissection to be a true hermaphrodite with a testis, epididymis, vas deferens and male accessory glands on the left side and an ovary, oviduct, uterus and male accessory glands on the right. In corneal mitoses there were 33 cells with 39 chromosomes and 8 cells with 40, and the animal was interpreted as an XO/XY mosaic. Its abnormalities could be explained by supposing that in the mouse XY cells determine a normal testis and XO ones a normal ovary.

ISSN:1424-8581    

DOI:10.1159/000130043

出版商:S. Karger AG    

年代:1969

数据来源: Karger

摘要:

A permanent human lymphoid cell line with 46 normal chromosomes and one minute marker chromosome was established from a normal human female. The abnormal karyotype was also present in a ‘direct’ three-day culture of the buffy coat and in a second permanent cell line derived from a later sampling of the donor’s leukocytes. The abnormality appears to be a persistent feature of the donor’s apparently mosaic karyotype and persists in the oldest culture line as a marker chromosome two years after establ

ISSN:1424-8581    

DOI:10.1159/000130044

出版商:S. Karger AG    

年代:1969

数据来源: Karger