摘要:

The toromere previously found by other workers in the distal end of the sixth chromosome (microchromosome) ofD. limmeiwas studied using differential staining ofDrosophila lummeigiant chromosomes. The toromere which was first described as a quinacrine-bright structure appears as a C-positive body. Quantitative cytofluorometric analysis showed highly significant increase in toromeric DNA under low temperature conditions.In situhybridization of125I nick-translatedD. virilissDNA (all three satellites were included in the sample) with polytene chromosomes ofD. lummeilarvae cultured at 12° C revealed no label incorporation into toromere region. Howeverin situhybridization of3H-RNA complementary to highly repetitious DNA ofD. lummeiandD. virilis(Cot = 10−1–10−2) with polytene chromosomes of the larvae cultured at 12° C coupled with banding studies enable us to conclude that the toromere probably contains an AT-rich repeated DNA. A well-developed toromere in the sixth chromosome of D.lummeiwas also demonstrated at normal temperature (25° C) in interspecific hybrids. The role of the toromere structure in the mitotic behavior of microchromosomes and their replication pattern is discussed.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797648

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

A detailed karyotype comparison amongR. cornutus cornutus, R. ferrumequinum nipponandR. luctus formosaeare made on the basis of relative length, G- and C-band patterns. The data presented here suggest strongly M.SM-1 and 2 inR. f. nipponwere formed by centric fusion of four of five small A-autosome pairs such as those in A-23∼25, 27 and 28 ofR. c. cornutus, while occurrence of M-SM-3 in the former was caused by pericentric inversion of a small A-pair such as that in A-24 or 25 of the latter, confirming the assumption described in our previous report (ANDŌet al.1980a). On the other hand, appearance of the secondary short arms of A-autosomes inR. f. nipponis attributable to the C-band material added to the telomeres of A-autosomes. Addition of heterochromatin is considered to have taken place also in the short arm of the ST-X chromosome inR. f. nippon, and to have brought about the morphological difference of the Y chromosome withinRinolophus.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797649

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

The standard B-chromosomes ofListera ovataare euchromatic, sub-metacentric and about half the size of the smallest autosomes. They are widespread in all populations throughout Europe. There are two derivative B-chromosomes, one sub-terminal type and a small telocentric type which are found sporadically in most populations. In Britain, the percentage of B-chromosomes per population varies from 89.12% to 62.82%. Populations found in wet habitats have about 14% more B-chromosomes than those found in normal habitats. There is a latitudinal bias in the percentage of B-chromosomes per population which range from an average of 21.81% for Central Italy, 42.85% for Switzerland, about 50% for Holland and 73.93% for Britain.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797650

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

The karyotypes of two species of grasshopper genusAcrotylusdiffer for the relative size of principally four chromosomes. C-banding differences between both species indicate that changes in both the heterochromatin content and the euchromatin content have occurred in the karyotypic evolution of these species.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797651

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

A comparative chromosome analysis ofAkodon longipilis, A. olivaceusandA. xanthorhinus(Rodentia, Cricetidae) was made. A similarity in diploid number (2n= 52), size, morphology, and G- and C-banding patterns was found.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797652

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

Somatic chromosomes of two Indian estuarine Catfishes,Plotosus canius(Plotosidae) andPseudeutropius atherinoides(Schilbeidae), were studied from kidney cells of both sexes. The diploid complement ofP. caniusincludes 36 chromosomes of which there are 5 pairs of metacentric, 5 pairs of submetacentric and 8 pairs of acrocentric nature (FN = 56). In the 2n= 58 karyotype ofP. atherinoides, there are 14 pairs of metacentric, 6 pairs of submetacentric, 1 pair of subtelocentric and 8 pairs of acrocentric chromosomes (FN = 98). No sex chromosomes were observed in either species. The results show that the family Plotosidae may be an exceptional group of Siluriformes characterised by low diploid numbers. The Schilbeidae, on the other hand, is evidently less divergent.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797653

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

The occurrence of nuclear vacuoles (membrane-bounded spaces) in the meiotic prophase nuclei of pollen mother cells in 23 species of Compositae was examined by electron microscopy. In nuclei of all examined species, nuclear vacuoles were recognized. These nuclear vacuoles were classified into four types by their size and appearance; 1) nuclear vacuoles which consist of many elongated tubes, 2) nuclear vacuoles which are large in size and few in number, 3) nuclear vacuoles which consist of elongated thin tubes with rather constant diameter, and 4) nuclear vacuoles which consist of few and thin elongated tubes. Nuclear vacuoles seemed to be a characteristic feature of each genus without any clear intergenus taxonomic relationship. Nuclear vacuoles were found not only in pollen mother cells but also in embryo sac mother cells of two examined species, suggesting that nuclear vacuoles are specific structures in meiocytes and that they are involved in the meiotic process though the nature of their contents in life remains unknown.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797654

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

In a series ofSolanumhybrids (2n= 24) studied meiosis was either normal, with regular formation of twelve bivalents per PMC, or else ten bivalents and a multiple chromosome association were present. Generally, these multiple associations were in the form of rings or chains of four, occasionally substituted by a chain trivalent and a univalent. Chromosome segregation at anaphase I and II was regular 12:12. Despite this, all hybrids were infertile, pollen sterility often exceeding 95%. Only the partially fertile F1S. indicumvar.multifloraXS. integrifoliumproduced F2progeny. In these F2plants multiple chromosome associations were observed in a fairly high frequency although such associations were not encountered in the corresponding F1. It is suggested that multiple chromosome homoeologies followed by pairing and crossing over in the F1could have resulted in the production of chromosomal interchanges in the F2. Despite regular synapsis and exchange leading to bivalent formation, segregational events at meiosis lead to the production of non-functional gametes in the F1's since those gametes with reconstituted parental genomes are expected to be functional.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797655

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

In the grasshopperValanga nigricornisa fusion between two telocentric autosomes, M8 and M9, is described which reduces significantly the chiasma frequencies of both the large and the medium members of the chromosome complement. This reduction was observed relative to both the normal spermatocytes within the single mutant individual as well as those in normal individuals from the same population sample. The meiotic behaviour of the fusion trivalent results in 50 per cent balanced gametes due to the random nature of its orientation at first metaphase of meiosis.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797656

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor

摘要:

Counting spermatocyte bivalents, we have determined the haploid numbern= 13 forDendrodoris limbataandDendrodoris grandiflora.The orders Nudibranchia and Notaspidea, possessing haploid values of 13 and 12 chromosomes respectively, seem to be more evolved than the other orders of the sub-class Opisthobranchia.

ISSN:0008-7114    

DOI:10.1080/00087114.1983.10797657

出版商:Taylor & Francis    

年代:1983

数据来源: Taylor