Cytogenetic Characterization of Two < b > < i > Metynnis < /i > < /b > Species (Characiformes, Serrasalmidae) Reveals B Chromosomes Restricted to the Females

Karyotypes and chromosomal characteristics with focus on B chromosomes of 2 species of the serrasalmid genusMetynnis, namelyM. lippincottianusand M. maculatus, were examined using conventional (C-banding) and molecular (FISH mapping of minor and major rDNAs andRex1,Rex3, andRex6 retrotransposable elements) protocols. Both species possessed a diploid chromosome number of 2n = 62 and karyotypes composed of 32 metacentric + 28 submetacentric + 2 subtelocentric and 32 metacentric + 26 submetacentric + 4 subtelocentric, respectively; one small B element was found in the female genome ofM. lippincottianus.C-banding revealed heterochromatin in the pericentromeric and terminal portions of all chromosomes of both species; the B chromosome was entirely heterochromatic. FISH showed 18S rDNA sites in 2 chromosome pairs in both species (pairs 19 and 22), and a large block in the B chromosome, while 5S rDNA signals were detected in the first pair of subtelocentric chromosomes in both species, moreover inM. maculatus an additional labeled pair 4 was observed. Mapping of theRex1,Rex3, andRex6 retrotransposable elements in the genomes ofM. lippincottianus andM. maculatus indicated that they were dispersed throughout nearly all the chromosomes of the complement, except for the B chromosome ofM. lippincottianus.Cytogenet Genome Res

Source: Cytogenetic and Genome Research - May 10, 2019 Category: Genetics & Stem Cells Source Type: research