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The stability of mutator (MR)-induced X-chromosomal recessive visible mutations in Drosophila melanogaster
Abstract:
In Drosophila, MR (male recombination) second chromosomes are known to act as mutators and recombination inducers in males. The induction of visible mutations by MR is observed at only a limited number of genes, such as singed bristle (sn), raspberry eye colour (ras), yellow body colour (y) and a carmine eye colour (car). Furthermore, sn mutations induced by MR are highly unstable, changing from a strong to a weak expression or reverting to the wild-type. It has been hypothesized by analogy with IS mutations in microorganisms, that MR-induced mutations also represent mutations of the insertion type. In this investigation the stability of two MR-h12-induced X-linked visible mutations was tested, one singed (snMR) and one raspberry (rasMR). The reversion frequency of both MR-induced mutations was low in the base population as well as upon outcrossing to C(1)DX, yw f females. The data reported here show that the MR-induced mutations become highly unstable when MR is re-introduced. The change of expression of an MR-induced mutation to a weaker phenotype or to the wild-type occurred at a frequency of 3.3 X 10(-3) (ras) to 20.4 X 10(-3) (sn). Recessive lethal mutations induced by MR in the X-chromosomes carrying the MR-induced singed or raspberry mutation were isolated and analysed. Among 11 independently MR-induced lethals in the rasMR-carrying X-chromosome, 4 were found to be allelic to a small deficiency that included the raspberry gene. 13 lethals were induced by MR in the snMR-carrying X-chromosome. Of these, 3 were located near the sn locus but none was allelic to a deficiency including the singed gene.
Insights
Male recombination (MR) second chromosomes in Drosophila induce mutations. MR-induced mutations, initially stable, become unstable when MR is reintroduced, suggesting insertion-type mutations. Lethal mutations were analyzed near singed and raspberry genes.
Area of Science:
- * Genetics
- * Molecular Biology
- * Drosophila melanogaster Research
Background:
- * Male recombination (MR) second chromosomes in Drosophila are known mutators and recombination inducers.
- * MR-induced mutations, particularly in genes like singed (sn) and raspberry (ras), exhibit instability.
- * Previous hypotheses suggest MR-induced mutations may be insertion-type, similar to IS mutations in microorganisms.
Purpose of the Study:
- * To investigate the stability of MR-h12-induced X-linked visible mutations (singed and raspberry).
- * To determine if MR-induced mutations exhibit instability upon reintroduction of MR.
- * To analyze recessive lethal mutations induced by MR in X-chromosomes carrying MR-induced singed or raspberry mutations.
Main Methods:
- * Tested the stability of two MR-h12-induced X-linked visible mutations: one singed (snMR) and one raspberry (rasMR).
- * Assessed reversion frequencies in a base population and after outcrossing to C(1)DX, yw f females.
- * Induced and analyzed recessive lethal mutations in X-chromosomes carrying MR-induced mutations.
Main Results:
- * MR-induced mutations showed low reversion frequencies in the absence of MR.
- * Reintroduction of MR significantly increased instability, with changes to weaker phenotypes or wild-type at frequencies of 3.3 x 10(-3) (ras) to 20.4 x 10(-3) (sn).
- * Analysis of lethals revealed that 4 out of 11 MR-induced lethals in the rasMR-carrying X-chromosome were allelic to a deficiency including the raspberry gene. Three of 13 lethals in the snMR-carrying X-chromosome were near the singed locus but not allelic to a deficiency.
Conclusions:
- * MR-induced mutations in Drosophila exhibit conditional instability, becoming highly mutable upon reintroduction of the MR element.
- * The instability and allelic relationships of induced lethals suggest a potential insertion mechanism for MR-induced mutations.
- * Further research is needed to elucidate the precise molecular mechanisms underlying MR-induced mutation and instability.