摘要:

Karyotypes are presented for three forms of the common ringtail opossum, Pseudocheirus peregrinus. These are tentatively regarded as the subspecies P.p. cookii, P.p. pulcher, and P.p. rubidus. In addition, we report for the first time the karyotype of the rock ringtail opossum, P. dahli. The three forms of P. peregrinus each have a diploid number of 2n = 20. C-banding studies indicate that the addition of large blocks of constitutive heterochromatin has played a major role in the evolution of all chromosomes in the karyotype. The X chromosome of P.p. pulcher is metacentric and approximately twice the relative size of the acrocentric X chromosomes of the other two forms of peregrinus. All three forms had two or three pairs of autosomes with secondary constrictions, a rare occurrence within the superfamily Phalangeroidea. P. (Pseudochirops) dahli has a diploid number of 2n = 16; a reduction in chromosome number may have occurred by Robertsonian fusions. Four of the eight chromosome pairs lack large blocks of C-band material and the secondary constrictions are located on the sex chromosomes.

ISSN:1424-8581    

DOI:10.1159/000131468

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Induction of sister chromatid exchanges (SCE) was examined as a function of post-embryonic development in C57BL/6J mice and Wistar rat bone marrow cells. At low concentrations of three different mutagens, cyclophosphamide, mitomycin C, and doxorubicin, induced SCE levels were not altered with post-embryonic development. However, at higher mutagen concentrations, SCE induction was significantly reduced in growing (3- to 8-week-old) animals when compared to mature (7- to 9-month-old) animals. Studies of 1- to 8-month-old mice at these high doses revealed that mutagen-induced SCE frequencies increase gradually during this period. These results suggest that with post-embryonic development, changes occur in cellular response to mutagen-induced DNA damage.

ISSN:1424-8581    

DOI:10.1159/000131469

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Cytogenetic and transmission data are given for a number of radiation-induced and spontaneous chromosomal changes which show that the Syrian hamster (Mesocricetus auratus) can tolerate a considerable amount of autosomal imbalance without phenotypic effect. It is suggested that the reason for this may lie in the very large amount of late-replicating chromatin present in this species.

ISSN:1424-8581    

DOI:10.1159/000131470

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The nonrandom pattern of the spatial arrangement of chromosomes in the human metaphase complement has been resolved into separate properties by statistical analysis of matrices of ranks of interchromosomal distances averaged over sets of 25 or 50 metaphases. Assessment of the effect of a mitotic-arresting agent, Colcemid, on each of the properties of the pattern shows that those properties for which a spindle fiber dependence may be postulated are disordered by Colcemid, while the tendency for the acrocentric chromosomes to associate, attributable to their mutual participation in nucleolar organization, is not impaired by Colcemid. Furthermore, this analysis has revealed that chromosomes 21 and 22 display an exceptional propensity to be generally associative, i.e., to be close to all chromosomes; that property is obliterated by Colcemid. Since a mitotic-arresting agent is routinely used in the preparation of cells for cytogenetic analysis, that property has hitherto not been recognized.

ISSN:1424-8581    

DOI:10.1159/000131471

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Cytogenetic analysis of a 15 month old girl evaluated for severe developmental delay and acral skeletal hypoplasia revealed a predominant 46, XX, r(15) karyotype. Prophase banding analysis showed minimal deletion of the ring chromosome (breakpoints pl2 and q26), while silver staining showed it to have an active nucleolus organizing region, multiple abnormal secondary configurations, and decreased satellite association. Although there was no spontaneous instability in the rest of the karyotype, gentian violet-induced chromosome breakage was significantly increased. The rate of spontaneous sister chromatid exchange was not elevated. Cellular mosaicism for chromosome 15 aneuploidy most likely accounts for the patient’s phenotypic abnormalitie

ISSN:1424-8581    

DOI:10.1159/000131472

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

We report here a silver stain technique (Kt stain) for locating the kinetochore (centromere body) without concomitant staining of C-band material. We compare our observations with those obtained from C-banding, Cd (centromeric dot) banding, and electron micrographs, and we report preliminary observations on Indian muntjac centromeres.

ISSN:1424-8581    

DOI:10.1159/000131473

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The reciprocal translocation T(5;12)31H, induced by irradiation of oocytes, causes sterility in most heterozygous male carriers, a tenfold reduction in mean sperm count, and a high frequency of abnormal sperm. Chromosome breakpoints are in bands 5B and 12F1, leading to a long (125) and a short (512) marker chromosome. Ninety five percent of germ cells showed chain quadrivalents or trivalents at meiotic metaphase I (MI). The order of loci on chromosome 5 is centromere—T31H—Rw—go with a recombination frequency of 31 + 7% between T31H and Rw. No linkage was found between T31H and linkage group XVI genes previously assigned to chromosome 12; it was concluded that they are located elsewhere. Viable tertiary monosomic and trisomic young (lacking the 512 region or with it in excess) were generated with post-natal frequencies of 4.5% and 14.6%, respectively, from outcrosses of heterozygous females. A deficiency of monosomics was also found in 11½ to 14½ day foetuses, when abnormal phenotypes or severe retardation produced by other unbalanced karyotypes were found. There was also a marked deficiency of monosomic offspring from outcrossed monosomic mothers, only 16.1% being found, whereas trisomic mothers gave 52.8% trisomic young. Surviving monosomics of both sexes were smaller than trisomics at birth and tended to have unusual skeletal fusions. Both types of aneuploid male were sterile, but tertiary monosomics were less severely affected, as judged by testis mass, sperm counts, and the appearance of testis sections. Both tertiary monosomic and trisomic females have smaller litters than normal females. Possible reasons for these findings are discussed, as well as recent observations throwing light on mechanisms of sterility in this type of transl

ISSN:1424-8581    

DOI:10.1159/000131474

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The banded chromosomes of the giant panda (Ailuropoda melanoleuca) and a hybrid bear (Ursus middendorfi × Thalarctos maritimus) have been studied and compared to those of other carnivores. The giant panda shares only a few apparently homologous chromosome arms with the bear (Ursidae) and equally few with the lesser panda, Ailurus julgens (Procyonidae). Chromosomal evidence suggests appropriate placement of the giant panda in a family separate from the Ursidae and the Procyonidae

ISSN:1424-8581    

DOI:10.1159/000131475

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

Cocultivation of plasma and lymphocytes from ataxia telangiectasia (AT) patients with those of normal individuals resulted in a significant increase in chromosomal damage in the normal cells. Tissue culture medium used to cultivate AT skin fibroblasts also significantly increased chromosome breakage in PHA-stimulated normal lymphocytes. This clastogenic effect was maximal when the “conditioned medium” was 8–9 days old. A similar effect was not observed with medium derived from normal skin fibroblasts. These observations suggest the presence of a clastogenic factor in the plasma of AT patients which may also be produced by AT skin fibroblasts in cu

ISSN:1424-8581    

DOI:10.1159/000131476

出版商:S. Karger AG    

年代:1980

数据来源: Karger

摘要:

The amount of ribosomal DNA in 12 infertile male carriers of Robertsonian translocations and in some of their fertile relatives with the same translocation or with a normal karyotype was determined by RNA/DNA hybridization. This was done to test the hypothesis that infertility results from the loss of ribosomal cistrons at the chromosome breaks and mendelian segregation of the remaining acrocentrics such that these subjects do not have threshold amount of rDNA. The mean saturation value for the infertile patients (0.0258%) was similar to that of the fertile carriers of the translocation (0.0262%) and of the relatives with a normal karyotype (0.0277%). The data do not support this hypothesis.

ISSN:1424-8581    

DOI:10.1159/000131477

出版商:S. Karger AG    

年代:1980

数据来源: Karger