Distribution of Telomeric DNA Sequences on the X-Radiation-Induced Chromosome Fragments Observed in the Genome of Androgenetic Brook Trout ( Salvelinus fontinalis , Mitchill 1814)

Cytogenetic screening of the androgenetic brook trout (Salvelinus fontinalis, Mitchill 1814) offspring hatched from eggs exposed to 420 Gy of X-radiation before insemination exhibited residues of the irradiated maternal nuclear genome in the form of small chromosome fragments. Remnants of the irradiated chromosomes had different sizes, and their number varied intraindividually from 1 to 15. To efficiently pass through the series of the cell divisions, such chromosome fragments must have had functional kinetochores. Distribution patterns of the telomeric hybridization signals on the chromosome fragments enabled us to distinguish their 3 groups: (i) telomere-less ring chromosomes with fused broken chromosome arms, (ii) rings formed in the course of fusion of the radiation-broken chromosome arm with the opposite telomeric region and exhibiting interstitial telomeric signals at the fusion point, and (iii) chromosome fragments with fused unprotected sister chromatids of 1 broken arm and intact telomeres from the other arm. Disturbances during segregation of such fragments, mainly breakages during anaphase, may partially explain intraindividual variation in the number and size of the chromosome fragments observed in the androgenetic brook trout.