摘要:

Studies were carried out on the male meiosis of Ellobius lutescens. The testicles of 29 male specimens were used for this purpose. Among 100 pachytene figures, 25 revealed an association between the sex vesicle and an autosomal bivalent of medium size, whereas in 75 figures the sex vesicle appeared as an isolated structure. The importance of this finding in relation to the proposed translocation of a segment of the Y chromosome to an autosome as well as the significance of this event in relation to a mechanism of sex determination in E. lutescens without zygote lethality is discussed.

ISSN:1424-8581    

DOI:10.1159/000129988

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

A 13-year-old girl selected for chromosome investigations because of mental deficiency and multiple malformations was found to be a 48, XXXX/ 49, XXXXX mosaic. Multiple sex chromatin bodies, up to four, were found in oral mucosa smears and in cultured fibroblasts. Two cells with drumsticks were found in scoring 1,000 granulocytes. Autoradiography revealed cells with three and with four late-replicating X chromosomes. Analysis of the patterns of replication along the individual late-replicating X chromosomes in each cell revealed a certain degree of asynchrony among them. In both types of cells, with four and five X’s, the long arms of the X were the last to terminate synthesis. In the occasional cell there was marked internal asynchrony in this respec

ISSN:1424-8581    

DOI:10.1159/000129989

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

In the present paper, additional data on the segregation of the three types of Robertsonian translocations which occur in man are considered. In both t(DqGq) and t(DqDq) there is a significant excess of balanced heterozygotes over chromosomally normal progeny among the offspring of male heterozygotes, and this is considered to provide further evidence for some form of prezygotic selection or meiotic drive (defined as the preferential recovery of one or more of the classes of gametes resulting from meiosis in a structural heterozygote) in man, the most likely mechanism being the preferential recovery of certain classes of spermatozoa. There is also a deficiency of unbalanced progeny, and the reasons for this are discussed. The frequency of spontaneous abortions among the progeny of all three translocations is not apparently increased over the frequency generally accepted for the population as a whole.

ISSN:1424-8581    

DOI:10.1159/000129990

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

The study deals with the results of a sex chromatin survey of all adult males and a chromosome survey of males selected because they were either 6 ft (183 cm) or more in height or were between 5 ft 10 in (178 cm) and 6 ft in height at an English hospital for mentally subnormal and psychiatric cases, in which a high proportion of patients are detained because of behavioural disturbances. In particular, the survey paid attention to the manner of admission and distinguished between men admitted via the Courts under the relevant sections of the British Mental Health Act of 1959 and those admitted informally. Sex chromatin of oral mucosa cells was examined in 917 men, and in 68 men chromosome analysis was conducted. Of the latter 19 were 6 ft or more in height and 49 were between 5 ft 10 in and 6 ft in height. Four of 82 men (4.7%) detained under the Mental Health Act were sex chromatin positive, by comparison with 7 of 824 (0.9%) informally admitted. Chromosome studies showed sex-chromosome aneuploidy in 5 of 19 men of 6 ft or more and in 2 of 49 between 5 ft 10 in and 6 ft. These findings are discussed in the light of other recent information on sex-chromosome aneuploidy, mental subnormality and aberrant behaviour.

ISSN:1424-8581    

DOI:10.1159/000129991

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

An identical nontranslocation autosomal mosaicism occurring in two consecutive generations is presented. A mother and two of her four daughters have been demonstrated to be 46/47 mosaics. The trisomic cells have an extra autosome in the 13–15, or D, group. The proband and one of her sisters reveal varying phenotypic expressions of the trisomic state. The mother and her two other daughters are phenotypically normal. The observation of 46/47 chromosomal mosaicism in man in a pattern which suggests that it is under genetic control necessitates the introduction of a new theory since it cannot be explained by earlier hypotheses which are directed towards understanding the chance occurrence of an individual mosaic. The rapidly accumulating evidence of the nonrandomness of chromosomal abnormalities points towards a possible defect in primary gene control of DNA replication. It is theorized that a gene which regulates the replication of a chromosome in the 13–15, or D, group is defective and that, as a result, this chromosome replicates twice instead of once during some, but not all mitoses, producing a mosaic of trisomic and normal cells. Presumably, the postulated mutant gene is present in the heterozygous state in the affected individuals and behaves as a dominant, with half of the children of an affected parent being abnor

ISSN:1424-8581    

DOI:10.1159/000129992

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

The chronology of DNA synthesis in homologous chromosomes was investigated autoradiographically and statistically. The statistical approach addressed itself toward establishing rigorously the occurrence of synchrony or antisynchrony in the autosomal pairs of groups A and E. In order to evaluate DNA synthesis more intimately, chromosome No. 2, whose short and long arms can be readily identified morphologically, was divided into five arbitrarily defined segments, and the autoradiographic behavior of these was determined. Neither consistent synchrony nor antisynchrony was found to characterize the group A homologs and the segments of No. 2. In contrast to the above findings, chromosomal pair 16 apparently replicated much of its DNA antisynchronously, and a suggestion of similar behavior was obtained for pairs 17 and 18. Nevertheless, exceptions for certain chromosomes at certain times in the S period were found, indicating synchrony or antisynchrony to be present under the conditions of the experiments. Even though no one simple and universal explanation appears to be compatible with the complex data presented, the results are compatible with metasynchronous replication of DNA in homologous chromosomes. This method of replication postulates a time gap of varying length between two homologous DNA loci on chromosomes, this time gap varying from locus to locus, from chromosome to chromosome and from time to time in the S period. Thus, the time length of exposure of cells to labeled thymidine plays a crucial and all-important factor in the type of data obtained autoradiographically and accounts for the diverse statements made in the literature regarding homolog replication.

ISSN:1424-8581    

DOI:10.1159/000129993

出版商:S. Karger AG    

年代:1968

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000129994

出版商:S. Karger AG    

年代:1968

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000129995

出版商:S. Karger AG    

年代:1968

数据来源: Karger