We found a match
Your institution may have access to this item. Find your institution then sign in to continue.
- Title
Ribosomal DNA Organization Before and After Magnification in Drosophila melanogaster.
- Authors
Bianciardi, Alessio; Boschi, Manuela; Swanson, Ellen E.; Belloni, Massimo; Robbins, Leonard G.
- Abstract
In all eukaryotes, the ribosomal RNA genes are stably inherited redundant elements. In Drosophila melanogaster, the presence of a Ybb- chromosome in males, or the maternal presence of the Ribosomal exchange (Rex) element, induces magnification: a heritable increase of rDNA copy number. To date, several alternative classes of mechanisms have been proposed for magnification: in situ replication or extra-chromosomal replication, either of which might act on short or extended strings of rDNA units, or unequal sister chromatid exchange. To eliminate some of these hypotheses, none of which has been clearly proven, we examined molecular-variant composition and compared genetic maps of the rDNA in the bb² mutant and in some magnified bb+ alleles. The genetic markers used are molecular-length variants of IGS sequences and of R1 and R2 mobile elements present in many 28S sequences. Direct comparison of PCR products does not reveal any particularly intensified electrophoretic bands in magnified alleles compared to the nonmagnified bb² allele. Hence, the increase of rDNA copy number is diluted among multiple variants. We can therefore reject mechanisms of magnification based on multiple rounds of replication of short strings. Moreover, we find no changes of marker order when pre- and postmagnification maps are compared. Thus, we can further restrict the possible mechanisms to two: replication in situ of an extended string of rDNA units or unequal exchange between sister chromatids.
- Subjects
RIBOSOMAL DNA; EUKARYOTES; DROSOPHILA melanogaster; CHROMOSOME replication; ELECTROPHORESIS; ALLELES; CHROMATIDS
- Publication
Genetics, 2012, Vol 191, Issue 3, p703
- ISSN
0016-6731
- Publication type
Article
- DOI
10.1534/genetics.112.140335