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Cytogenetic Evidence for Asexual Evolution of Bdelloid Rotifers
Jessica L. Mark Welch, David B. Mark Welch and Matthew Meselson
Proceedings of the National Academy of Sciences of the United States of America
Vol. 101, No. 6 (Feb. 10, 2004), pp. 1618-1621
Published by: National Academy of Sciences
Stable URL: http://www.jstor.org/stable/3371238
Page Count: 4
You can always find the topics here!Topics: Cosmids, Chromosomes, DNA probes, Genomes, Embryos, Diploidy, Species, Signals, Polyploidy, Biological evolution
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DNA sequencing has shown individual bdelloid rotifer genomes to contain two or more diverged copies of every gene examined and has revealed no closely similar copies. These and other findings are consistent with long-term asexual evolution of bdelloids. It is not entirely ruled out, however, that bdelloid genomes consist of previously undetected pairs of sequences so similar as to be identical over the regions sequenced, as might result if bdelloids were highly inbred sexual diploids or polyploids. Here, we employ fluorescent in situ hybridization with cosmid probes to determine the copy number and chromosomal distribution of the heat shock gene hsp82 and adjacent sequences in the bdelloid Philodina roseola. We conclude that the four copies identified by sequencing are the only ones present and that each is on a separate chromosome. Bdelloids therefore are not highly homozygous sexually reproducing diploids or polyploids.
Proceedings of the National Academy of Sciences of the United States of America © 2004 National Academy of Sciences