Please use this identifier to cite or link to this item: http://hdl.handle.net/1946/4386
Threshold traits are responsible for a number of inheritable phenotypic characteristics in organisms, yet their nature remains elusive and they have proven hard to study. Here we show the wing shape of Drosophila melanogaster, genetic perturbations and morphometic analysis can be used to investigate the genetic and developmental underpinnings of threshold characters. The E1 allele of the Egfr gene was used to study the genetic and developmental aspect of threshold characters. An association between a mutation in the Egfr promoter and the relative placement of the two crossveins was also re-evaluated. More than a hundred inbred strains were crossed to two strains with the same Egfr-E1 allele; strain 5144 and strain 1564. Results showed that the extra veins form in specific parts of the wing, not randomly all over and are seemingly independently of extra veins in other parts of the wing. Results also showed that cross allowed for the presence of the extra vein, and sex seemed to determine both its presence and length. The association between the Egfr polymorphism and the C region was confirmed. An association between the Egfr polymorphism and the formation of extra veins was found, however this depends on the genetic background and the sex of the individual. It was determined that the same regulatory SNP affects the continuous trait and the manifestation of a threshold trait and implicates the role of Egfr signalling in both placement of veins, and also in the formation of the vein material.
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