摘要:

Nesokia indica, the Indian mole rat, exhibits extensive variability (polymorphism) for the constitutive heterochromatin of the X and Y chromosomes. These polymorphic X and Y types range from a large metacentric chromosome to a small acrocentric one and occur in different frequencies in the population. On the assumption that there is random mating among individuals carrying these various X and Y chromosomes, the population shows Hardy-Weinberg proportions for the genotypes. However, notwithstanding the partial or total loss of constitutive heterochromatin of the X and Y chromosomes in a few individuals, its retention in most of the animals seems obligatory to the population at large. Hence, we suggest that the C-heterochromatin plays a “regulatory” role in the population dynamics of this spec

ISSN:1424-8581    

DOI:10.1159/000131873

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Diploid-triploid chimeras have been observed both in man and in a number of laboratory and livestock animals. The mechanism(s) of their origin remains enigmatic. One approach is to calculate for each proposed mechanism the expected frequencies of zygotes bearing different gonosomic complements in the two cell lines. Observed samples are then compared with the expectations. The mechanisms that have been considered include: (1) fertilization of a blastomere, (2) absorption of the second polar body into a blastomere, (3) fertilization of the first polar body, (4) independent fertilization of both nuclei in binucleated oocytes, (5) fertilization of the second polar body as well as the egg, and (6) fusion of two eggs. The sample of minks comprised three preimplantation embryos, nine postimplantation embryos, and three neonatal pups, with gonosomic complements of 7 XX/XXX, 3 XX/XXY, 4XY/XXY, and 1 XY/XYY; the chicks comprised 13 embryos at 1 day of incubation, 1 embryo at 4 days, and one adult bird, with gonosomic complements of 5 ZZ/ZZZ, 1 ZZ/ZZW, 1 ZW/ZZZ, 3 ZW/ZZW, and 5 ZW/ZWW. If it is assumed that within each species all, or most, of the 2n/3n chimeras arise from the same mechanism, then the occurrence of a type that has an expected frequency of zero for a given proposed mechanism effectively eliminates that mechanism as a source. All of the chicks could have resulted from only one mechanism, viz., independent fertilization of both nuclei in binucleated oocytes. The sample of minks could have resulted from the same mechanism or from fertilization of a blastomere of a two-cell, 2n embryo.

ISSN:1424-8581    

DOI:10.1159/000131874

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Somatic and germ cells of the gray short-tailed opossum (Monodelphis domestica) were analyzed cytogenetically by C-banding, G-banding, and silver staining. The diploid chromosome number was found to be 18. C-banding revealed constitutive heterochromatin at the centromeres of all chromosomes, with additional heterochromatin on one arm of the Y. Silver staining for the localization of nucleolus organizer regions (NORs) showed NORs on the X and on a pair of autosomes, tentatively designated as chromosome 5. In females, the NORs on both X chromosomes were active in 98.3% of all somatic cells analyzed, indicating that this locus escapes sex-chromosome dosage compensation. Chromosome 5 showed an active NOR in only 16.2% of cells scored from the six females. In males, 100% of the somatic cells analyzed showed an active NOR on the X chromosome. Greater variability of autosomal NOR activity was observed between male individuals and between different tissues of the same male. Silver staining of pachytene spermatocytes revealed that (1) only an autosomal NOR was active, whereas the NOR of the X chromosome was inactive, and (2) the X and Y chromosomes showed asynaptic behavior, even though all autosomal synaptonemal complexes were fully formed during this stage.

ISSN:1424-8581    

DOI:10.1159/000131875

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

A detailed technique is described for obtaining preparations of the chromosome complements of human sperm by fertilization of hamster eggs and analysis of the male pronucleus. Some of the more difficult aspects and important steps are emphasized. Technical data from 17 consecutive experiments are presented to provide an estimate of the number of karyotypes which can be obtained in an experiment.

ISSN:1424-8581    

DOI:10.1159/000131876

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The kinetics of germ-cell development were examined in random-bred adult Swiss mice by means of tritium autoradiography. Comparisons were made between males with normal (+/+) and abnormal karyotypes: Rb(l 1.13)4Bnr/+ and T(1;13)70H/+ heterozygotes, T70H tertiary trisomies, andT70H translocation trisomies. The time taken for the first wave of labelled cells to progress from premeiotic S-phase to diplotene and then on to the second meiotic metaphase was estimated in each stock, and rates of increase of labelled meiotic figures were measured. The S-phase to diplotene interval did not differ significantly among the different genotypes, taking from 10 days, 16 h to 10 days, 19 h. In Rb4Bnr/+, T70H translocation trisomic, and T70H tertiary trisomic males, however, labelled meiotic figures accumulated at a lower rate, particularly in the tertiary trisomies. A cell delay for some meiocytes was thus indicated during meiotic prophase. A correlation was seen between the degree of meiotic delay and severity of reduction in sperm count. The period from late diplotene to metaphase II was also found to be longer in T70H tertiary trisomies than in controls (+/+) or other chromosomally abnormal males.

ISSN:1424-8581    

DOI:10.1159/000131877

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Somatic cell hybrids between SV40-transformed human fibroblast cells and normal human fibroblasts were isolated and tested for growth in vitro and in athymic nujnu (nude) mice. All hybrid cells formed by a cross of WI-18/VA-2, a tumorigenic SV40-transformed human fibroblast, with IMR-90 expressed T antigen and grew in the appropriate selective medium. However, tumorigenic potential ranged from completely suppressed to fully expressed in these hybrid cells. In addition, all hybrid cells formed between LNSV, a nontumorigenic SV40-transformed human fibroblast, and IMR-90 were nontumorigenic. Previous studies have shown that the tumorigenic potential of hybrids cells formed between a variety of human tumor cell lines and normal human fibroblasts is completely suppressed. These results imply that the genetic control of tumorigenic expression in virally transformed human cells differs from that seen in spontaneously arising human tumor cells.

ISSN:1424-8581    

DOI:10.1159/000131878

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The karyotypes of 10 different species of the family Muridae (Acomys airensis, Arvicanthis niloticus, Hylomyscus stella, Malacomys longipes, Mastomys huberti, Myomys daltoni, Mus musculus, Rattus norvegicus, Thamnomys gazellae, and Uranomys ruddi) are compared by different banding techniques. From a reconstruction of the presumed ancestral karyotype of the Muridae the sequence of the various rearrangements leading to the present karyotypes is proposed in order to determine their phylogenetic relationships. In particular, the present karyotypes of the mouse and rat differ from the ancestral one by at least 12 and 7 rearrangements, respectively. A clear tendency for accumulation of a specific type of rearrangement in a given branch of the cladogram is observed. In regard to the mouse, a large number of translocations, with break points situated in the proximal part of the long arms, have occurred, which conserved the acrocentric form of the ancestral chromosomes but led to multiple recombinations of the bands.

ISSN:1424-8581    

DOI:10.1159/000131879

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

The reciprocal translocations T(X;4)37H and T(X;11)38H were induced by acute X-irradiation of spermatozoa. Male heterozygotes are completely aspermic with a spermatogenic block at pachytene and testis masses about one third of normal, though metaphase I is very occasionally reached in T37H. For both translocations the X chromosome breakpoints are in band XA2, and the autosomal breakpoints are in 4D3 for T37H and 11E1 for T38H, leading to long and short marker chromosomes. Chain quadrivalents predominated in oocytes at MI, with no rings; there were 32% trivalent + univalent configurations in T37H and 40% in T38H. These generated (1) XO mice, (2) tertiary trisomies carrying 20 bivalents and the small X4 (T37H) or X11(T38H) markers. These trisomies were apparently lethal in T37H but sub-viable in T38H and sometimes fertile as XX11 and trisomic XXX11 females, though sterile as XX11 Y males. However, many developed exencephaly in utero, probably because of the distal duplication on chromosome 11. No tertiary monosomies were found in 12 to 14 day embryos. Seven percent of all female progeny were XO, with a higher than expected frequency in T37H and a lower than expected one in T38H. T37H is about two units and T38H about five units from the spf locus on the X chromosome with evidence for some crossover suppression between the T38H breakpoint and Ta. Autosomal linkages found were T37H-ra-6 (R.F. of 16 + 4% between T37H and m) and T38H-/Rewc (R.F. of 5 + 3%). T37H/+ females weighed about 10% less than normal females at birth and about 30% less at weaning; there was little if any effect in T38H/+ females or in males carrying either translocation. Neither translocation had any marked effect on viability. T37H/ + females showed variegation when heterozygous for b with the wild type allele in the long 4X marker. On average, about 20% of the coat was brown rather than black. However, no clear evidence for m variegation was found.

ISSN:1424-8581    

DOI:10.1159/000131880

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Silver-stained preparations of cultured lymphocytes obtained from 12 pure-bred dogs revealed the presence of nucleolus organizer regions (NORs) on four to seven chromosomes in females and five to eight chromosomes in males. All seven males had a NOR on the Y chromosome. The telomeric location of the NORs on the autosomes suggested by an earlier study was confirmed.

ISSN:1424-8581    

DOI:10.1159/000131881

出版商:S. Karger AG    

年代:1983

数据来源: Karger

摘要:

Using a procedure in which human sperm were allowed to fertilize zona-free golden hamster (Mesocricetus auratus) eggs in vitro, the sperm chromosomes of a man heterozygous for inv(3) (p1 1 q 11) were analyzed. When the chromosomes were Q-banded, the inverted chromosome had the bright centromeric band on the short arm rather than on the long arm, as was seen in the normal No. 3. One hundred and eleven sperm chromosome spreads were examined, of which 64 contained the normal chromosome and 47 the inverted one. This was not significantly different from the expected 1:1 ratio. No sperm containing a chromosome imbalance caused by a crossover within the inversion were seen. Ten (8.1%) of the sperm contained chromosome abnormalities unrelated to the inversion. The ratio of X- to Y-bearing sperm was 55:45.

ISSN:1424-8581    

DOI:10.1159/000131882

出版商:S. Karger AG    

年代:1983

数据来源: Karger