摘要:

A suspension is made in isotonic (2.2%) sodium citrate solution from the contents of the tubules from a whole testis or a testicular biopsy specimen. The germinal cells are sedimented by centrifuging, leaving most of the sperm in the supernatant fluid, which is discarded. The cells are resuspended in hypo-tonic (1%) sodium citrate solution and left to stand at room temperature for 12 minutes, after which they are sedimented again and fixed as a concentrated suspension in a mixture of 3 parts absolute ethyl alcohol to 1 part glacial acetic acid plus a trace of chloroform. Two quick changes into fresh fixative follow. Air-dried preparations are made from the final fixed suspension and stained in lactic-acetic-orcein. The method is suitable for stages of male meiosis in which the chromosomes are condensed. Its principle advantage is the separation of the clumps of spermatogonia and spermatocytes into individual cells which are randomly dispersed over the preparations. Compared with squash techniques, the air-drying method gives improved spreading of the chromosomes and less cell breakage.

ISSN:1424-8581    

DOI:10.1159/000129818

出版商:S. Karger AG    

年代:1964

数据来源: Karger

摘要:

Preparations were obtained from the testes of six sterile males of the T(X; ?) 16H stock. 81.7% of 694 primary spermatocytes in stages from diakinesis to first metaphase contained chain quadrivalents composed of a terminal Y chromosome and three other elements that were distinguishable in length. A normal XY pair was not seen in any cell. These observations and others indicate that the stock carries an unequal reciprocal translocation between the X chromosome and one of the shortest autosomes, the break points being approximately median in both chromosomes. This suggests that the locus of tabby (Ta), which is known to be closely linked with the breakage point, lies near the middle of the X chromosome.

ISSN:1424-8581    

DOI:10.1159/000129819

出版商:S. Karger AG    

年代:1964

数据来源: Karger

摘要:

Female mice heterozygous for the sex-linked gene tabby (To) normally show a striped or variegated coat pattern resulting from random inactivation of one or other X-chromosome. In a stock descended from an irradiated female this variegation did not occur and heterozygotes for tabby looked wild-type. This led to the hypothesis that the wild-type allele of Ta had been translocated to an autosome and so was remaining active in all cells; the presence of a reciprocal X-autosome translocation was then demonstrated cytologically. A similar suppression of variegation was found for two other sex-linked genes, bent-tail (Bn) and blotchy {Bld), and also for both tabby and blotchy in crossover animals which had the mutant alleles on their translocated X-chromosomes. In these animals the mutant allele was fully expressed and the wild-type allele not at all. This showed that, in addition to the translocated X being active, the normal X was inactive in all cells, and demonstrated that the variegated effect in normal heterozygous females depended on the randomness of X-inactivation. Linkage tests suggested that the order of loci in the X chromosome was Bn-bteak-Ta-Blo, but this was not firmly established. The autosome involved in the translocation has not yet been identified.

ISSN:1424-8581    

DOI:10.1159/000129820

出版商:S. Karger AG    

年代:1964

数据来源: Karger

摘要:

Cytological and histological studies on ovaries from cattle fetuses of various stages indicate that the factor leading oöcytes in first meiotic prophase to enter dictyotene is contact with follicular cells. Early in embryonic development, each ovigerous cord in the upper layer of the ovarian cortex appears to contain a disproportionately greater number of germ cells than potential follicular cells. Many of these oöcytes enter meiosis and proceed beyond diplotene to diakinesis, only to degenerate. As the fetal ovary develops, the correct ratio of germ cells to potential follicular cells is gradually established, from deep in the cortex upward. An individual oöcyte in first meiotic prophase is now surrounded by a single dense layer of follicular cells; only these oöcytes are capable of entering dictyotene and forming primordial follicles. Precocious oöcyte maturation appears to be forestalled by the intimate contact of the follicular cells, which seems to force the oöcyte nucleus to maintain the non-homologous association of its biva

ISSN:1424-8581    

DOI:10.1159/000129821

出版商:S. Karger AG    

年代:1964

数据来源: Karger

摘要:

An Xg(a+) male with XXYY sex chromosomes was the son of an Xg(a+) father and an Xg(a—) mother with normal chromosomes. This seems to be the first example in which there is good evidence of non-disjunction at the first and second meiotic division of paternal spermatogenesis, giving rise to an XYY sperm which fertilized a normal ovum. Other explanations are discusse

ISSN:1424-8581    

DOI:10.1159/000129822

出版商:S. Karger AG    

年代:1964

数据来源: Karger

摘要:

The diploid chromosome number of the Indian five striped squirrel {Funambulus pennanti, Wroughton) is 54 with a preponderance of acrocentric chromosomes. On the basis of chromosome number and morphology the interrelationships of the different species of squirrel are discussed.

ISSN:1424-8581    

DOI:10.1159/000129823

出版商:S. Karger AG    

年代:1964

数据来源: Karger

摘要:

The pattern of DNA synthesis in the chromosomes of Group 4–5 has been analysed in cells from individuals with the cri du chat syndrome. The abnormal chromosome, a No. 5, is one of the pair characterized by relatively early completion of synthesis in the long arms. The two remaining members of this group, characterized by extensive late replication throughout their lengths, therefore may now be recognized as the Nos.

ISSN:1424-8581    

DOI:10.1159/000129824

出版商:S. Karger AG    

年代:1964

数据来源: Karger