摘要:

The sequence of centromere separation in late metaphase/anaphase cells from a long term culture of cells from a male rat-kangaroo, Potorus tridactylus, was studied. The karyotype of the PTK-1 line has five pairs of autosomes, one modified No. 1 (M1), and X, Y1 and Y2. In 87% of the cells the centromeres of No. 4 or 5 were among the first to separate. Y1, Y2, X, or the marker, M1, were not the earliest chromosomes to separate. Y2 separated last most frequently (59%), followed by X, M1 and Y1. The overall relative averages for the sequence of separation in the entire genome (centromere separation index or CSI) are 1.52, 1.40, 1.11, 0.92, 0.88, 0.86, 0.68, 0.56, and 0.27 for 5, 4, 2, 1, Y1, 3, M1, X, and Y2, respectively (the average for the whole genome is 1). The data indicate that the centromeres of the chromosomes of Potorus separate in a specific, genetically controlled, non-random sequence. The chromosomes separating late have larger amounts of centromeric heterochromatin; all of this or part of it may be the controlling element for the sequence of separation.

ISSN:1424-8581    

DOI:10.1159/000131638

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

An analysis of the nucleolar organizer region (NOR) by silver staining of five species of the order Gymnotiformes, Gymnotus carapo, Apteronotus albijrons, Sternopygus macrurus, Eigenmannia virescens, and Eigenmannia sp., is reported. The five species presented only one pair of homologs bearing NORs. In G. carapo, A. albijrons, and S. macrurus the silver-stained NORs were present as small black dots over the chromosomes. In E. virescens, the short arm of one of the largest chromosome pairs was entirely stained with silver. Eigenmannia sp. presented an intraspecific variability of the NOR-bearing pair and an increase in the length of this region, the larger one being about six times the size of the smaller. These findings suggest that an increase in the number of ribosomal genes in the NORs of certain species occurred during the evolution of this group.

ISSN:1424-8581    

DOI:10.1159/000131639

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Male mice were treated with graded doses of methyl methanesulfonate (MMS) and mated with untreated female mice during the six to ten days after treatment. The nature of the primary lesions induced in late spermatids was investigated by analysing the types and rates of chromosome aberrations in the first cleavage metaphases. The chromosome aberrations recovered at the first cleavage were predominantly of the chromosome-type. Their frequency increased exponentially with increasing dose of MMS. The results suggested that the nonenzymatic conversion of DNA containing alkylated bases to new damage, possibly strand breaks, during the maturation and storage of sperm was primarily responsible for the enhancement of the frequency of chromosome-type aberrations.

ISSN:1424-8581    

DOI:10.1159/000131640

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Chiasma frequency and the distribution of chiasmata within chromosomes 1, 2, and 9 were investigated in a total of seven males with presumptively normal meiosis. With the exception of one unusual individual, there was little variation among the males examined for these characteristics. The exceptional male had a reduced chiasma frequency, which, rather than being considered abnormal, was thought to represent the lower end of the normal range of variability. A statistical analysis of the histograms of chiasma distribution confirmed the impression of overall similarity, and we conclude that genetic maps of these chromosomes may now be constructed without too much disturbance from differences between individuals. The maps will be presented separately in a subsequent paper.

ISSN:1424-8581    

DOI:10.1159/000131641

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

The ZW sex chromosomes of the European eel, Anguilla anguilla, and the American eel, A. rostrata, were examined with C-band and fluorescent staining to demonstrate the C-band heterochromatin. The W as well as Z chromosomes in both species are C-band negative except for a small amount of C-band heterochromatin in the centromeric region, in contrast to the W or Y elements of most other vertebrates. No fluorescing W-associated body is evident either in interphase nuclei or in metaphase plates. The ZW chromosomes of the two species have substantially similar size, morphology, and patterns of C-band heterochromatin. Karyologic and evolutionary implications are discussed.

ISSN:1424-8581    

DOI:10.1159/000131642

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

A monocentric and submetacentric Y/Y translocation without evidence of mosaicism was observed in a male with tall stature and azoospermia. Chromosome measurements of the abnormal Y of this patient and the normal Y of his father were undertaken to determine more precisely the chromosome break points in this translocation. The measurements failed to show a definite loss of chromatin from the original short arm of the proband’s Y chromosome. The azoospermia and infertility in our patient, in contrast to his father, suggest that infertility may be associated with this specific Y/Y translocation in human male

ISSN:1424-8581    

DOI:10.1159/000131643

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

A heteromorphism in a pair of macrochromosomes in male Siebenrockiella crassicollis is interpreted as an XX/XY sex determining system. The heteromorphism involves a difference in centromere position and amount and distribution of heterochromatin. The only other sex chromosome system known in turtles is found in the kinosternid genus Staurotypus and is also an XX/XY system, but it involves a different chromosome pair and different chromosomal rearrangements. These two systems have independently arisen within the suborder Cryptodira and share no common ancestry. The sex chromosome system in Siebenrockiella represents a relatively early stage of differentiation. It differs from the hypothesized steps of differentiation in having a heterochromatically derived X.

ISSN:1424-8581    

DOI:10.1159/000131644

出版商:S. Karger AG    

年代:1981

数据来源: Karger

摘要:

Twenty eight American mink × Chinese hamster somatic cell hybrids were analysed for the expression of mink enzymes and for mink chromosomes. The results of this analysis made it possible to assign the genes for phosphoglucomutase-1 and phosphogluconate dehydrogenase to chromosome 2, those for lactate dehydrogenase A and glucose phosphate isomerase to chromosome 7, and those for lactate dehydrogenase B and triosephosphate isomerase to chromosome 9

ISSN:1424-8581    

DOI:10.1159/000131645

出版商:S. Karger AG    

年代:1981

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000131646

出版商:S. Karger AG    

年代:1981

数据来源: Karger