摘要:

Chromosome studies of testicular cells corroborated an earlier report of only seven chromosomes in somatic cells of males of the Indian muntjac, Muntiacus muntjak. The heterotrivalent observed during meiosis confirmed the view that a translocation had occurred between the X and an acrocentric autosome. Thus the male has an XYY, sex-chromosome system.

ISSN:1424-8581    

DOI:10.1159/000130171

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

Three of the seven currently recognized bisexual polyploid anuran species have morphologically very similar diploid “cryptic species” counterparts. The North American diploidtetraploid cryptic species pair Hyla chrysoscelis and H. versicolor is analyzed and compared with diploid and tetraploid populations of the South American nominal species Odontophrynus americanus. It is postulated that, through an intermediate triploid stage, tetraploidy could arise independently in diploid species by way of suppressed maturation in oöcytes. Tetraploid populations arising sympatrically from diploid species may maintain their integrity bio-acoustically. Polyploidization in the Anura is an important evolutionary mechanism and may prove to be quite wide spread when species are carefully examined on a population l

ISSN:1424-8581    

DOI:10.1159/000130172

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

The results of comparative studies of the efficacy of phytohemagglutinin (PHA-P) and pokeweed mitogen (PWM) as mitotic stimulators for in vitro cultures of mouse lymphocytes are reported. These studies have established that clearly defined optimal concentration ranges exist for each mitogen and that higher than optimal levels of either mitogen exert an inhibitory effect on cell proliferative activities. The levels of mitotic stimulation achieved with peripheral-blood cultures and with cultures of lymph-node lymphocytes should facilitate a variety of cytogenetic studies not heretofore practicable with the mouse.

ISSN:1424-8581    

DOI:10.1159/000130173

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

A method is described for karyotypic sexing of cultured mouse blood cells, using both the morphological and the late-replicating properties of the Y chromosome. The misclassification rate is low, even when metaphase plates of poor quality are included.

ISSN:1424-8581    

DOI:10.1159/000130174

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

Somatic pairing of homologous chromosomes of Diptera insect cells is maintained in long-term tissue culture. In prophase and prometaphase the pairing extends throughout the length of the chromosomes and resembles meiotic pachytene. By metaphase the homologs are associated only in the pericentromeric areas, which persists through anaphase. The material is an excellent model for studies of this process and balanced somatic crossingover, which it permits.

ISSN:1424-8581    

DOI:10.1159/000130175

出版商:S. Karger AG    

年代:1972

数据来源: Karger

摘要:

The time sequence of DNA synthesis of autosomal constitutive heterochromatin and euchromatin was studied in kidney-cell cultures of the European hedgehog which had been pulse labeled with 3H-thymidine. The mean length of the S-period is 10.4 h for euchromatin and 5.2 h for constitutive heterochromatin. Thus the latter replicates DNA twice as fast as euchromatin. Constitutive heterochromatin starts replicating DNA about 7 h later and finishes 1.5 h later than euchromatin. The asynchrony of DNA synthesis between the two types of chromatin is particularly marked in the beginning of the S-phase. The inactive X chromosome also synthesizes DNA faster than euchromatin; it begins a short time before and finishes slightly after constitutive heterochromatin. The finding of accelerated DNA synthesis in autosomal heterochromatin lends itself to several possible explanations, although it remains difficult to understand fully at present.

ISSN:1424-8581    

DOI:10.1159/000130176

出版商:S. Karger AG    

年代:1972

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130177

出版商:S. Karger AG    

年代:1972

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130178

出版商:S. Karger AG    

年代:1972

数据来源: Karger