ISSN:1424-8581    

DOI:10.1159/000130719

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The presumed random and independent process of human chromosome segregation in man-mouse somatic cell hybrids was studied. The results of chromosome analysis on 196 cells from 15 related hybrid strains have provided the first convincing evidence that segregation of human chromosomes can be nonindependent and often concordant. Different human chromosomes were not retained with equal frequency in these hybrid clones. Some were present in 80 % of all the cells, whereas others appeared in less than 10 % of the same cells. Linear regression analysis was used to test for correlation of the frequencies of all pair-wise combinations of human chromosomes present in these hybrid clones. Twenty-two of 136 possible correlations were statistically significant, indicating that concordant segregation of particular pairs of human chromosomes is a rather frequent occurrence.

ISSN:1424-8581    

DOI:10.1159/000130720

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

Quadriradial (QR) configurations from four different human lymphocyte meta-phase samples have been analyzed: a patient with Fanconi’s anemia; normal female cells X-irradiated with 150 or 200 R in S or G2; spontaneous QRs occurring in 13,584 metaphases; and cells from two sibs with Bloom’s syndrome. That mitotic chiasmata are caused by crossing-over rather than by random breakage and reunion was concluded from the following observations: (1) In the spontaneous sample, mitotic chiasmata are about as frequent as all other QRs together. (2) The frequencies of mitotic chiasmata and of other QRs are not correlated in the different samples. (3) The break points in other QRs are situated at random relative to chromosome length, whereas the distribution of chiasmata is highly nonrandom. (4) Although the centromeres of chromatid translocations occur in alternate and adjacent positions with approximately equal frequencies, there are very few adjacent counterparts to mitotic chiasmata. These can best be interpreted as a result of an abnormal U-type rejoining of chromatids in a chiasma. (5) Chiasmata found in heteromorphic chromosome pairs show that crossing-over has, indeed, taken pl

ISSN:1424-8581    

DOI:10.1159/000130721

出版商:S. Karger AG    

年代:1976

数据来源: Karger

摘要:

The successive use of several banding methods permitted us to compare the karyotypes of six Malagasy lemurs: Microcebus murinus, Lemur fulvus fulvus, L. f. collaris, L. f. albocollaris, L. macaco, and L. mongoz. A correspondence can be found among all clearly identifiable chromosomes. Based on rearrangements of some of the chromosomes, the karyotype of M. murinus seems to be closest to that of the hypothetical common ancestor. The karyotype of L. f. fulvus, which is nearly identical to that of M. murinus, gives rise to those of other forms by several rearrangements.

ISSN:1424-8581    

DOI:10.1159/000130722

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130723

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130724

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130725

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130726

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130727

出版商:S. Karger AG    

年代:1976

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130728

出版商:S. Karger AG    

年代:1976

数据来源: Karger