Caenorhabditis Globin genes: Rapid intronic divergence contrasts with conservation of silent exonic sites |
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Authors: | Andrew P Kloek James P McCarter Robert A Setterquist Tim Schedl Daniel E Goldberg |
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Institution: | (1) Departments of Molecular Microbiology and Medicine, Howard Hughes Medical Institute, Washington University School of Medicine, 600 S. Euclid Ave., 63110 St. Louis, MO, USA;(2) Department of Genetics, Washington University School of Medicine, 660 S. Euclid Ave., 63110 St. Louis, MO, USA;(3) Department of Biochemical and Biophysical Sciences, University of Houston, 77204-5934 Houston, TX, USA |
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Abstract: | Globin genes from theCaenorhabditis speciesbriggsae andremanei were identified and compared with a previously describedC. elegans globin gene. The encoded globins share between 86% and 93% amino acid identity, with most of the changes in or just before
the putative B helix.C. remanei was found to have two globin alleles,Crg1-1 andCrgl-2. The coding sequence for each is interrupted by a single intron in the same position. The exons of the two genes are only
1 % divergent at the nucleotide level and encode identical polypeptides. In contrast, intron sequence divergence is 16% and
numerous insertions and deletions have significantly altered the size and content of both introns. Genetic crosses show thatCrg1-1 andCrgl-2 segregate as alleles. Homozygous lines for each allele were constructed and northern analysis confirmed the expression of
both alleles. These data reveal an unusual situation wherein two alleles encoding identical proteins have diverged much more
rapidly in their introns than the silent sites of their coding sequences, suggesting multiple gene conversion events.
Correspondence to: D. Goldberg |
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Keywords: | Alleles Evolution Gene conversion Introns Nematode |
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