ISSN:1424-8581    

DOI:10.1159/000129951

出版商:S. Karger AG    

年代:1967

数据来源: Karger

摘要:

The chromosomes of the field mouse Akodon azarae have been investigated. In males the diploid chromosome number is 38, with XY sex chromosomes. The four types of chromosome constitution in females are as follows: (a) 38 chromosomes with XX sex chromosomes; (b) 38 chromosomes Xx, the x being a grossly deleted X chromosome; (c) 38/37 Xx/XO sex chromosome mosaic; and (d) 37 chromosomes with an XO sex chromosome complement. This variability in females is believed to result from a dosage compensation mechanism ranging from X chromosome inactivation to total elimination of the X chromosome.

ISSN:1424-8581    

DOI:10.1159/000129952

出版商:S. Karger AG    

年代:1967

数据来源: Karger

摘要:

In the Chinese hamster comparison of heterochromatic and euchromatic arms of X1 and X2 chromosomes and an autosomal pair (No. 3) of similar length by means of relative regression coefficients has indicated that the heterochromatic, or late-replicating, elements vary less per unit length than euchromatic elements of similar length and, therefore, do not maintain a constant percentage of the total complement length.

ISSN:1424-8581    

DOI:10.1159/000154943

出版商:S. Karger AG    

年代:1967

数据来源: Karger

摘要:

A family possessing two mongoloid sibs and three balanced heterozygous carriers for a non-centric translocation between the long arm of a No. 21 and long arm of a No. 22 chromosome, yielding a medium-size acrocentric marker, is presented. In addition, the mother of the propositi, her brother and mother possessed a small, satellited centric fragment which is presumed to be the reciprocal element of the translocation.

ISSN:1424-8581    

DOI:10.1159/000154936

出版商:S. Karger AG    

年代:1967

数据来源: Karger

摘要:

Experiments with human lymphocytes and H.Ep.2 human neoplastic cells treated with tritiated thymidine yielded evidence which suggests that sister chromatid crossing-over may occur in the centromere. As a result of this study a possible mechanism of isochromosome formation is postulated.

ISSN:1424-8581    

DOI:10.1159/000154937

出版商:S. Karger AG    

年代:1967

数据来源: Karger

摘要:

A simple method is described by which sex chromatin can be studied in the cells of the external root sheath of single hairs. From a human capital hair many thousands of scorable nuclei can be obtained. Since this material is suitable for orcein staining, preparations are ready for analysis within a few minutes. Qualitative and quantitative results are presented from control persons and multiple-X individuals. The method is most convenient for studies in various mammals, and samples of results are given for some rodent and carnivore species.

ISSN:1424-8581    

DOI:10.1159/000154938

出版商:S. Karger AG    

年代:1967

数据来源: Karger

摘要:

The DNA content was measured in individual polytene chromosomes of Chironomus tentans belonging to the two last classes of replication. The following results were obtained: (1) The DNA contents of the chromosomes of the higher size class were about twice that of the lower class, which indicates that most or all of the chromatids carry out one replication between these two stages. (2) The DNA contents were found to be correlated to chromosome length, and the average amount of DNA per band was similar in the four chromosome pairs. (3) The probable DNA value per chromatid set was determined, from which the average DNA value per chromomere could be estimated to 10-16 g. This value corresponds to about 105 base pairs, suggesting either that the bands represent operational units of great complexity or that a large part of DNA is non-functional in an informational sense.

ISSN:1424-8581    

DOI:10.1159/000154939

出版商:S. Karger AG    

年代:1967

数据来源: Karger

摘要:

The autoradiographic behavior of normal male and female chromosomes in blood leukocytes at various stages in the DNA synthesis period (S period) has been investigated with 3H-thymidine. One X chromosome in female cells and the Y in male cells do not replicate their DNA or do so to a limited extent, 12 h before metaphase, when most of the other chromosomes are undergoing replication at a substantial rate. Asynchrony among the chromosomes is evident at that time. Furthermore, the X in female cells and the Y in male cells are the last chromosomes to finish their DNA replication. The replication of an elongated No. 1 autosome in a patient with primary amenorrhea has been compared to that of its normal homolog. The secondary constriction area, particularly prominent in the elongated No. 1, is the last area to finish replication in both the abnormal and normal No. 1 autosomes and is one of the latest segments in the human complement to finish replication. The leukocyte generation time was found to be 18 h or more in the presence of phytohemagglutinin (PHA). The data presented further delineate the time sequence and pattern of chromosomal replication in normal human leukocytes.

ISSN:1424-8581    

DOI:10.1159/000154940

出版商:S. Karger AG    

年代:1967

数据来源: Karger

摘要:

The frequency of sex chromatin positive nuclei was determined in oral mucosa smears of 47 newborn females during their first three days of life. In contrast to some previous reports, the lowest sex chromatin frequency found was 21 %, and the means for days 1, 2 and 3 were 33.5 %, 34.1 %and 37.0% respectively. The mean value for day 3 was nearly identical with that obtained for six normal adult women. The slight increase over the three days was statistically significant, although the magnitude of this increase was much less than that reported by other workers. By determining the ratio of nuclei with morphologic characteristics suitable for sex chromatin determinations to those which do not meet minimal morphologic criteria, it was possible to show that there are more unsuitable, probably degenerating nuclei present shortly after birth than later on. This factor may explain the low initial frequencies other workers have reported. It may be difficult to differentiate some degenerated nuclei from viable nuclei. The former may be ‘false negatives’, and their inadvertent inclusion in a count would decrease the frequency of sex chromatin positive nuclei. This argument is supported by our findings on sex chromatin counts performed in the absence of selection criteria. Smears with many unsuitable nuclei had a much lower frequency than those with few unsuitable nuclei. This bias can be reduced, if not eliminated, when stringent selection criteria are applied. With standard criteria, reproducible and reliable sex chromatin frequency determinations can be made on oral smears of newborn infa

ISSN:1424-8581    

DOI:10.1159/000154941

出版商:S. Karger AG    

年代:1967

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000154942

出版商:S. Karger AG    

年代:1967

数据来源: Karger