Possible Common Origin of B Chromosomes in Neotropical Fish (Siluriformes, Auchenipteridae) Reinforced by Repetitive DNA Mapping

Abstract The aim of this paper was to present the second case of B chromosomes in Auchenipteridae (Trachelyopterus sp.), and to test the hypothesis that the B chromosomes of this species and Parauchenipterus galeatus might have a common origin, since these two species have phylogenetic proximity. Both species have 58 chromosomes in the A complement, heterochromatin preferentially located at terminal region of the most of chromosomes, simple Ag-NORs located at the short arm of a subtelocentric pair, which was confirmed by hybridization with 18S rDNA, two submetacentric pairs carrying 5S rDNA sites, and presence of B chromosomes. The B chromosomes of the two species are small, metacentric, and almost totally heterochromatic, with variation of number intra and interindividual. In addition, for the first time in fish, the telomeric sequence [TTAGGG]n was dispersed along the B chromosomes (both species). The [GATA]n microsatellite were scattered in all chromosomes of the A complement and absent in the B chromosomes, in both species. These aspects confirm the phylogenetic proximity between the genus Parauchenipterus and Trachelyopterus, and they suggest the hypothesis that the B chromosomes of the two species might have common origin, previous to the diversification of these genera.

Quantitative Analysis Of Random Chromosomal Aberrations In PHA-Stimulated Blood and Bone Marrow / 대한임상병리학회지

BACKGROUND: Chromosomal aberration observed only in a few metaphases may cause the cytogeneticists to have difficulties in making a decision whether it is due to in vivo mosaicism/multiple clones or due to in vitro artifact. This is especially important when the chromosome of concern has been associated with a classical chromosome syndrome, malignancy or its evolution. Therefore, we aimed to establish a range for random chromosomal aberrations among cells from PHA-stimulated blood(PB) and bone marrow(BM) cultures. METHODS: Among the cells from 449 PB and 472 BM specimens referred for chromosome studies from 1997 to 1998, we analyzed the frequency of random aneuploidy, structural abnormalities, and breaks/gaps. RESULTS: The number of cells analyzed was 5,904/4,488(1997/1998) in PB and 4,211/4,124(1997/1998) in BM. The frequency of metaphases with random chromosomal aberrations of BM(32.10%) was much higher than that of PB(5.90%). The most frequent aberration was chromsome loss. Autosome losses were inversely correlated with autosome size(correlation coefficient = -0.83 and -0.72, p<0.01), smaller chromosomes being lost more frequently while autosome breaks/gaps were correlated with autosome size(correlation coefficient = 0.69 and 0.85, p<0.01), in PB and BM. Comparing the data from 1998 to the data from 1997, the frequency of chromosome losses(<0.5% in PB, <2.25% in BM), gains(<0.1% in PB and BM), breaks/gaps(<0.1% in PB, <0.25% in BM), and structural aberrations(