摘要:

We have studied the evolution of the karyotype of 6 tetraploid strains ofChinese hamsterinduced with colchicine. All six strains have lost with time a certain number of chromosomes, and each one of them has become stabilised on an average number, characteristic for each strain. The analysis of the karyotype of these six strains showed that different types of chromosomes behave in different ways; in particular a decrease was observed in the large and mediummchromosomes and in thestchromosomes; thetchromosomes, the smallmchromosomes and the minute chromosomes either remained unchanged with time or increased. It was also observed that while the large and mediummchromosomes are generally in a triploid number the other vary considerably in number from cell to cell. This causes a large variability of the karyotype of different cell populations. In these populations we could not observe the presence of a « stemline » in the classical meaning of this term.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796416

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

From a pseudotetraploid strain ofChinese hamster, induced with colchicine and having an average of 40 chromosomes per cell, two strains having chromosome numbers of around 70–74 were induced with a second treatment. About one year after treatment, the chromosome numbers of these two lines decreased to an average of 52.7 and 54.6.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796417

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

DNA cytophotometry has been used to study the development of the female gametophyte ofGinkgo biloba.It has been found that, at the beginning of the cellular stage, a large part of the cell population of the gametophyte is not haploid as to DNA content. Namely, very few nuclei (about 5%) show IC DNA content (i.e.the content of an haploid cell in the presynthetic stage of the mitotic cycle), while about 50% show 2C DNA content, more than 40% 4C and the remaining 8C and higher contents.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796418

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

Along with chromosome aberrations,137Cs gamma-irradiation in high doses induces chromatid aberrations in the pre-synthetic phase G1of the naturally synchronized cell population of embryonic radicles inC. capillarisseeds. This occurs in seeds with an artificially decreased moisture content.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796419

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

摘要:

The karyotype of the Brazilian lizardPolychrus spshowed 2n=20 chromosomes for the female and 2n=19 chromosomes for the male. The meiotic cells of the male in diakinesis and metaphase I showed 8 bivalents and 1 trivalent. In metaphase II there were cells withn=9 chromosomes, and cells withn= 10 chromosomes. The sex determining mechanism was interpreted as belonging to the « pseudo XO/XX » type, which differs from the X1X2Y/X1X1X2X2type because the Y is morphologically indistinguishable from the X2chromosome. This is the second occurrence of this case to be described in the vertebrates.

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796420

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor

ISSN:0008-7114    

DOI:10.1080/00087114.1971.10796421

出版商:Taylor & Francis    

年代:1971

数据来源: Taylor