Association between Chromosomal Inversion Polymorphisms and Accumulation of Recessive Deleterious Mutations in Drosophila melanogaster
Date Issued
2012
Date
2012
Author(s)
Tung, Shih-Fan
Abstract
Chromosomal inversion polymorphisms have been demonstrated to play adaptive roles in natural populations by capturing local co-adapted alleles within recombination-suppressed regions of inversion heterozygotes. On the other hand, a less studied but important role of inversion polymorphisms is that recombination suppression by heterozygous chromosomal rearrangement may accumulate recessive deleterious mutations and thus cause a great amount of mutation load. Deleterious mutations will be eliminated when homozygotes and in turn increase heterozygosity of various inversions. The Afrotropical population of Drosophila melanogaster with high chromosomal inversion heterozygosity and high ratio of recessive lethals provides an ideal material to test any association between them by examining the accumulation pattern of recessive lethals. Recessive lethals are predicted to locate near the inversion breakpoints where the recombination is greatly suppressed by inversion heterokaryotypes. By using recombination and deficiency mappings, 14 recessive lethal alleles from eight lethal-bearing third chromosomes (each from eight distinct isofemale lines, respectively) were identified. All of recessive lethals were mapped into the regions close to (less than 3 centi-Morgan) the inversion breakpoints which were polymorphic in the African population. This result clearly shows that recessive lethal alleles are accumulated by recombination suppression and distributed non-randomly along inverted chromosomes. The data also provide the strong association between chromosomal inversions and the accumulation of recessive deleterious mutations.
Subjects
genetic load
inversion breakpoint
Muller’s ratchet
recessive lethal
recombination-suppression
Type
thesis
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