摘要:

Chromosome replication at the beginning and termination of the S period in a primary culture of embryonic human fibroblasts has been studied through the use of 3H-thymidine labeling and autoradiography. In the analysis the observed numbers of silver grains above chromosomes were compared with those expected on the assumption of uniform labeling throughout the whole chromosome complement. The S period began almost simultaneously in all chromosomes but No. 1 (in which synthesis began very early) and the Y (in which it began late). The chromosomes terminate their replication asynchronously; Nos. 2, 3, 4–5 and 19–20 terminate DNA synthesis early, while Nos. 1, 16, 21–22 and the Y replicate late. The results obtained have been compared with published data on DNA replication in cultured peripheral blood leucocytes. The differences found in chromosome replication (especially in that of Nos. 1 and 2) may be due to differences in the function of these chromosomes in the two cell

ISSN:1424-8581    

DOI:10.1159/000129996

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

The pattern of DNA synthesis in human chromosomes at the beginning and termination of the S period has been analyzed in a primary culture of embryonic fibroblasts. 3H-thymidine pulse labeling and autoradiography have been used. For analysis of intrachromosomal asynchrony of DNA replication, each chromosome was subdivided, depending on its length, into five to nine equal regions, for which the number of silver grains was determined at the beginning and termination of the S period. Four types of replication sequences of regions along the chromosome were found: (1) replication begins from both telomere regions of the chromosome and terminates in the centromere and adjoining regions (chromosomes Nos. 1 and 3); (2) replication begins in the telomere region of the long arm and terminates in the centromere region and in the short arm (Nos. 13–15, 17–18 and 21–22); (3) replication begins from the telomere regions of both arms and terminates simultaneously in all regions along the chromosome (No. 2); (4) there are two types of regions in chromosomes – telomeric and centromeric – from which duplication begins and in which it terminates, i.e., the process of DNA replication in them continues throughout the whole S period (centromere region of Nos. 4–5, 16, 17 and 19–20; telomere regions in Nos. 4–5, 17 and 18). The possible factors which control the sequence of DNA replication in regions along the chromosom

ISSN:1424-8581    

DOI:10.1159/000129997

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

The rabbit karyotype is divided into 11 groups on the combined basis of the arm ratio and relative length of the chromosomes. This division is compared with rabbit karyotypes derived by other authors. Radioautographic techniques are used as an aid to the identification of the sex chromosomes. Chromosome preparations from mitotic cells of pre-implantation embryos and from adult rabbit biopsy specimens are analysed. Techniques are described by which chromosome preparations may be obtained from pre-implantation embryos and for the rapid culture of adult rabbit tissues. Attention is drawn to an accurate method of chromosome measurement.

ISSN:1424-8581    

DOI:10.1159/000129998

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

A study was made of the first meiotic prophase in the female germ cells of the golden hamster (Mesocricetus auratus). It was found to commence immediately after birth, and all the germ cells had entered the diplotene stage by day 9 postpartum. The period during which the germ cells synthesised DNA was determined using an autoradiographic technique, and was found to be restricted to the first four days after birth.

ISSN:1424-8581    

DOI:10.1159/000129999

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

The anatomic, histologic and cytogenetic findings on a bovine true hermaphrodite are discussed. The XX/XY chimerism in various tissues, including the kidney and testicular tissue of the ovotestis, combined with the presence of a uterus, cervix, vagina, seminal vesicles, penis and ovary provide evidence for dispermic fertilization involving two ova or an ovum and its nonextruded polar body. Circumstantial evidence regarding the mechanism of freemartinism is discussed.

ISSN:1424-8581    

DOI:10.1159/000130000

出版商:S. Karger AG    

年代:1968

数据来源: Karger

摘要:

The hybrid duck resulting from the mating of a Muscovy male and a White Pekin female is sterile. Utilizing a technique for the culture of blood cells, chromosome preparations were made of the parental and hybrid ducks. Morphological differences were found to exist between the first and fourth pairs of chromosomes of the Muscovy and the White Pekin. The first pair of chromosomes has a long-to-short arm ratio of 2:1 in the Muscovy and 1.6:1 in the White Pekin. The sex chromosome pattern of both species was found to be ZZ/ZW, rather than ZZ/ZO, with the Z and the W occupying relatively the same positions in the different ducks. The fourth pair of chromosomes, representing the sex chromosomes of the male duck, possesses short arms in the White Pekin but not in the Muscovy. This difference in morphology is probably significant with reference to the sterility of these hybrids. Studies of the gonads have indicated that gametogenesis does not proceed past the first stage in meiosis. Synapsis of homologous chromosomes from the two parent species evidently does not occur because of differences in morphology.

ISSN:1424-8581    

DOI:10.1159/000130001

出版商:S. Karger AG    

年代:1968

数据来源: Karger

ISSN:1424-8581    

DOI:10.1159/000130002

出版商:S. Karger AG    

年代:1968

数据来源: Karger