The Drosophila maternal effect mutant, bicaudal (bic), affects the anterior-posterior axis of the embryo. It is incompletely penetrant, producing a variety of lethal embryonic phenotypes, the most severe of which is replacement of the anterior half with a mirror image duplication of the posterior half. Genetic mapping has placed this locus within a region defined by the overlap of two chromosomal deficiencies on the second chromosome. Indirect genetic evidence has suggested that a lethal mutation that maps to the same region, $vr22\sp{P3}$ may represent a more severe allele of the bicaudal locus. A chromosome walk was performed in this region and over 65 kb of overlapping clones isolated. The location of the P-element insertion responsible for the $vr22\sp{P3}$ mutation was localized in the walk, and cDNAs corresponding to two adjacent transcription units isolated. These clones have been analyzed and sequenced, and one shows at least a 65% identity with eukaryotic release factor.
Recombination work with bicaudal mutant stocks has improved penetrance of the mutation to a level allowing genetic analysis. These stocks were used in genetic rescue experiments to determine the locations of bic and $vr22\sp{P3}.$ The results of genetic rescue and polymorphism mapping provide good evidence that $vr22\sp{P3}$ and bicaudal are in fact alleles at the same locus, and the gene codes for a protein with strong homology to release factor. The bic protein most likely plays a role in negative regulation of translation of downstream maternal genes such as nanos.
| Identifer | oai:union.ndltd.org:RICE/oai:scholarship.rice.edu:1911/16622 |
| Date | January 1993 |
| Creators | Gajewski, Kathleen Mary |
| Contributors | Beckingham, K. M. |
| Source Sets | Rice University |
| Language | English |
| Detected Language | English |
| Type | Thesis, Text |
| Format | 161 p., application/pdf |
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