Structural and functional evidence that a B chromosome in the characid fish Astyanax scabripinnis is an isochromosome

Article Abstract:

Both structural and functional evidence that a B chromosome in the characid fish Astyanax scabripinnis is an isochromosome has been found by analyzing localization of a repetitive DNA sequence on both B chromosome arms and synaptonemal complex formation to test the functional homology of both arms. Tandem repeats were almost symmetrically located in the arms of the B chromosome except for two additional small clusters proximal on the slightly longer arm. The two arms seem to form chiasmata. The hypothesis that the B chromosomes are isochromosomes that have arisen by centromere misdivision and chromatid nondisjunction was tested. Fluorescence in situ hybridization (FISH) localized the repetitive DNA into noncentromeric constitutive heterochrmatin.

Physiological aspects, DNA, Sister chromatid exchange

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Altitudinal variation of B chromosome frequency in the characid fish Astyanax scabripinnis

Article Abstract:

Variation in B chromosome frequency relative to altitude has been studied in three populations of the characid fish Astyanax scabripinnis. The macro B chromosome was in the two high-altitude populations, in the most appropriate environment for the species, but not in the population from a lower altitude which is at the ecological limit for the population. Because of geography, gene flow can be downstream only. The best explanation is the parasitic model of B chromosome evolution as opposed to the heterotic model.

Chromatin, Evolution (Biology), Evolution, Altitude, Influence of

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Physical distribution of SINE elements in the chromosomes of Atlantic salmon and rainbow trout

Article Abstract:

Analysis of physical distribution of short interspersed repetitive elements (SINEs) in salmon and rainbow trouts reveal that SINEs are interspersed throughout the chromosal area except for the heterochromatin-positive areas.

Atlantic salmon, Rainbow trout

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