Pairs Of Telocentric Chromosomes Research Articles

Variation of Giemsa C-band and fluorochrome banded karyotypes, and relationships inAllium subgen.Molium

The somatic karyotypes of 10 taxa belonging toAllium subgen.Molium (Liliaceae) from the Mediterranean area have been investigated using Giemsa C-band and fluorochrome (Hoechst, Quinacrine) banding techniques. A wide range of banding patterns has been revealed. InAllium moly (2n = 14),A. oreophilum (2n = 16) andA. paradoxum (2n = 16) C-banding is restricted to a region on each side of the nucleolar organisers and the satellites show reduced fluorescence with fluorochromes. The satellites are also C-banded and with reduced fluorescence inA. triquetrum (2n = 18), but two other chromosome pairs also have telomeric bands which are not distinguished by fluorochrome treatment. InA. erdelii (2n = 16) 4 pairs of metacentric chromosomes have telomeric C-bands while 2 pairs of telocentric chromosomes have centromeric C-banding. InA. subhirsutum (2n = 14),A. neapolitanum (2n = 28),A. trifoliatum subsp.hirsutum (2n = 14) andA. trifoliatum subsp.trifoliatum (2n = 21) chromosomes with long centromeres, consisting of a centromere and nucleolar organiser are positively C-banded on each side of the constriction. InA. subhirsutum banding is confined to the pair of chromosomes with this feature, whereas inA. neapolitanum one additional chromosome pair has telomeric bands and inA. trifoliatum there are varying numbers of chromosomes with centromeric and telomeric bands, depending on the subspecies.A. zebdanense (2n = 18) shows no C-bands. The banding patterns in this subgenus are compared with those recorded for otherAllium species and with the sectional divisions in the genus. Evidence from the banding patterns for allopolyploidy inA. trifoliatum subsp.trifoliatum andA. neapolitanum is discussed.

Karyological relationships in turtles (Reptilia: Chelonia).

The mitotic chromosomes of 33 species of chelonians representing 22 genera and six families were investigated. Chromosome number and morphology are the same for most members of a given family and range from 66 in Trionyx to 34 in Pelomedusa. Most emydid genera have 50 chromosomes. The karyotype of Chelydra (2n = 52) is similar to those of some testudinid and emydid genera and is unlike the 56 chromosome karyotype of kinosternid turtles. The three genera of tortoises examined, Gopherus, Testudo, and Geochelone, have 52 chromosomes, but Gopherus differs in karyotypic details. The karyotype of Geochelone is like that of Chelydra and the 52 chromosome genera of emydid turtles. The African pleurodiran Pelomedusa has three additional pairs of small acrocentric or telocentric chromosomes not present in the earlier described karyotype of Podocnemis. Examination of meiotic chromosomes revealed frequencies of chiasmata formation similar to those reported earlier. Sex chromosomes were not distinguishable.

CHROMOSOME-NUMBER VARIATIONS IN THE RAINBOW TROUT (<i>SALMO GAIRDNERII IRIDEUS</i> (GIBBONS))

The somatic chromosomes of the rainbow trout from two localities of Hokkaido are studied by the routine air-drying method. One of six specimens studied has 58 chromosomes consisting of 23 pairs of meta- and submetacentrics, one pair of subtelocentric and 5 pairs of telocentric chromosomes. The remaining five specimens show a basic number, 2n, 60. The arm number of both groups is 104, and this seems to indicate polymorphism resulted from the Robertsonian system.

SOMATIC ASSOCIATION OF CHROMOSOMES IN BARLEY

Distances between pairs of homologous and nonhomologous telocentric chromosomes were measured in root tip cells of barley. The nonhomologous telocentrics were randomly distributed, whereas the homologues were significantly closer than would be expected with random distribution.

Cytogenetic studies of the somatic and germ-line cells in sand rats (Psammomys obesus).

The chromosomes in both somatic and germ-line cells of the sand rat (Psammomys obesus) were studied. The diploid number of chromosomes was 48. The autosomes consisted of 4 pairs of large metacentric chromosomes, 10 pairs of medium to small metacentric and submetacentric chromosomes and 9 pairs of telocentric chromosomes. The X chromosomes in both sexes were the largest of the entire complement. The Y chromosome was a mediumsized metacentric chromosome. The two X chromosomes in the female cells were similar in size and morphology but differed in the DNA replication pattern. Studies of the meiotic chromosomes in the male germ-line cells revealed 23 autosome bivalents and the sex chromosomes either as an XY bivalent or X and Y univalents.

Intraspecific Chromosome Variation In The Bat, Macrotus Waterhousii Gray

The karyotypes of two subspecies of bat, Macrotus waterhousii Gray (Phyllostomatidae), have been studied and compared. Specimens of M. water¬housii mexicanus from Morelos and Guerrero, Mexico, as well as specimens in one sample of M. waterhousii californicus from Sonora, had a karyotype with a diploid number of 46 including a telocentric Y-chromosome in the male complement. An¬other sample of M. waterhousii californicus from Sonora, as well as samples from Arizona and California, had a diploid number of 40. Of these samples, the Arizona specimens also revealed a telocentric Y-chromosome and in addition a secondary constriction on the supposed X-chromosome, whereas the California sample was characterized by a pronounced achromatic region near the centromere on one of the large pairs of telocentric chromosomes and the existance of a meta or submetacentric Y-chromosome in the male. This appears to be the first major karyo type variation of bats reported at the subspecific level.