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Genes 2018, 9(12), 610;

Genomic Characterization of a B Chromosome in Lake Malawi Cichlid Fishes

Department of Biology, University of Maryland, College Park, MD 20742, USA
Author to whom correspondence should be addressed.
Received: 3 November 2018 / Revised: 28 November 2018 / Accepted: 30 November 2018 / Published: 5 December 2018
(This article belongs to the Special Issue Evolution, Composition and Regulation of Supernumerary B Chromosomes)
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B chromosomes (Bs) were discovered a century ago, and since then, most studies have focused on describing their distribution and abundance using traditional cytogenetics. Only recently have attempts been made to understand their structure and evolution at the level of DNA sequence. Many questions regarding the origin, structure, function, and evolution of B chromosomes remain unanswered. Here, we identify B chromosome sequences from several species of cichlid fish from Lake Malawi by examining the ratios of DNA sequence coverage in individuals with or without B chromosomes. We examined the efficiency of this method, and compared results using both Illumina and PacBio sequence data. The B chromosome sequences detected in 13 individuals from 7 species were compared to assess the rates of sequence replacement. B-specific sequence common to at least 12 of the 13 datasets were identified as the “Core” B chromosome. The location of B sequence homologs throughout the genome provides further support for theories of B chromosome evolution. Finally, we identified genes and gene fragments located on the B chromosome, some of which may regulate the segregation and maintenance of the B chromosome. View Full-Text
Keywords: supernumerary chromosomes; B chromosomes; next-generation sequencing; coverage ratio analysis supernumerary chromosomes; B chromosomes; next-generation sequencing; coverage ratio analysis

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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited (CC BY 4.0).

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Clark, F.E.; Conte, M.A.; Kocher, T.D. Genomic Characterization of a B Chromosome in Lake Malawi Cichlid Fishes. Genes 2018, 9, 610.

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