摘要:

The chromosomes of Rattus (Mastomys) nataknsis (2n = 36) can be classified into four groups. On the basis of the location of centromeres, the 17 pairs of autosomes include three morphological groups: six pairs subterminal, five pairs submedian to median and six pairs terminal. The sex chromosomes C3nstitute the fourth group. The X chromosome is the largest and the Y is one of the largest in the entire complement. Chromosome replication patterns in R. nataknsis were studied using autoradiography after 3H-thymidine incorporation in cultured embryonic and bone marrow cells and in vivo bone marrow cells. In female cells, replication is later for one whole X chromosome, the long arm of the other X, one pair of small metacentrics and one pair of small telocentrics than for the other parts of the complement. In male cells, replication is late for the long arm of the X, the presumptive Y, and the same two pairs of autosomes as in female cells. There is no obvious difference between the replication patterns of cells in vivo and in vitro. Cell generation time, however, is shorter in vivo. The asynchronous replication patterns of the sex chromosomes in R. natalensis are similar in general but different in detail in relation to those in cultured cells of the Chinese and Syrian hamsters.

ISSN:1424-8581    

DOI:10.1159/000129974

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

A pericentric inversion has been discovered in one branch of a family, in which a 21/22 translocation of the usual type had been transmitted through three generations. The female carrier of the translocation with inversion appears to be phenotypically normal. She has, however, an obvious tendency to develop aneuploid offspring.

ISSN:1424-8581    

DOI:10.1159/000129975

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

DNA synthesis in diploid human cells was studied at the cellular and chromosomal levels by means of 3H-thymidine labeling and autoradiography. It was observed that the rate of DNA synthesis increased slowly at the beginning and decreased rapidly at the end of the S period, with a peak midway in the period. The rate and duration of DNA synthesis in individual chromosomes were found to be characteristic for each chromosome pair. Even though there is a certain tendency for the longer chromosomes to have a longer S period, enough variation existed to indicate that the structural make-up of the chromosomes may play an important role in the rate and length of time during which chromosomal DNA synthesis occurs.

ISSN:1424-8581    

DOI:10.1159/000129976

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

The pattern of initiation of DNA replication in normal male and female human cells was studied by a modified method of Mukherjee and Sinha (1965). One of the X chromosomes of female and the Y chromosome of male cells were found to begin DNA replication definitely later than other chromosomes. The possible cause of the discrepancy among reported studies was discussed.

ISSN:1424-8581    

DOI:10.1159/000129977

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

Chromosomes were analyzed from five subspecies of the ground squirrel, Spermophilus townsendi. The diploid chromosome number was 46 in S. t. vigilis and S. t. canus, 38 in S. t. idahoensis and S. t. mollis and 36 in S. t. townsendi. A chromosomally homogenous population of ground squirrels, separated from S. t. townsendi by the Yakima River and having 38 instead of 36 chromosomes, was recognized as a new subspecies, S. townsendi nancyae. Chromosomal evidence linked with zoogeography suggest that the subspecies of S. townsendi radiated from an ancestral population (2n = 46), probably originating in Oregon, with eventual spread north across the Columbia River (S. t. townsendi and nancyae) and southeast into Idaho, Utah and Nevada (S. t. mollis and idahoensis). Robertsonian centric fusion rather than dissociation of metacentric chromosomes receives strong zoogeographic support as the mechanism responsible for karyotype evolution in S. townsendi.

ISSN:1424-8581    

DOI:10.1159/000129978

出版商:S. Karger AG    

年代:1968

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000129979

出版商:S. Karger AG    

年代:1968

数据来源: Karger