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Recessive lethal mutations within the bithorax-complex in Drosophila
Abstract:
Genetic deficiencies of the bithorax-complex (BX-C) in Drosophila, have been used to recover recessive lethal mutations in this chromosome region following mutagenesis. Complementation analysis separates these lethal mutations into five groups within a smaller deficiency, thought to remove the entire BX-C, and into 20 to the left and 4 to the right of the region. Homozygotes for each of only three groups of lethals, Ubx, abdA and AbdB, produce homoeotic segmental transformations in embryos. The functional domains of abdA and AbdB have been defined by changes in the appearance of larval hypodermal structures and of clones in imaginal tissue. The function abdA is required in all the compartments caudal to the anteroposterior border of abdominal segment 1 up to and including the anterior region of abdominal segment 8, whilst AbdB is required in abdominal segments 5 to 9. One allele of AbdB produces a ninth abdominal setal band and structures characteristic of head segments posterior to A8. Rare adult survivors hemizygous for an AbdB allele have eight abdominal segments in both sexes, and lack genitalia in females. Our findings are discussed in the context of the organisation of genetic functions within the BX-C.
Insights
Mutagenesis of Drosophila's bithorax-complex (BX-C) identified lethal mutations. Three key genes (Ubx, abdA, AbdB) cause embryonic segmental transformations, defining functional domains within the BX-C.
Area of Science:
- Developmental Biology
- Genetics
- Molecular Biology
Background:
- The bithorax-complex (BX-C) in Drosophila controls segment identity.
- Understanding BX-C function is crucial for deciphering developmental gene regulation.
Purpose of the Study:
- To identify and characterize recessive lethal mutations within the BX-C region.
- To define the functional domains of specific BX-C genes, including abdA and AbdB.
Main Methods:
- Mutagenesis to generate recessive lethal mutations.
- Complementation analysis to group mutations.
- Analysis of embryonic and adult phenotypes, including homoeotic transformations and imaginal tissue clones.
Main Results:
- Lethal mutations were mapped relative to BX-C deficiencies.
- Homozygotes for Ubx, abdA, and AbdB mutations exhibited homoeotic segmental transformations.
- Functional domains for abdA (segments 1-8) and AbdB (segments 5-9) were delineated.
- Specific AbdB alleles caused transformations to segment 9 and head structures, with survivors showing reduced segmentation and absent genitalia.
Conclusions:
- Genetic deficiencies of BX-C are effective in isolating lethal mutations.
- The study precisely maps functional domains of abdA and AbdB genes.
- Findings contribute to understanding the organization and function of the BX-C in segment specification.