Studies on Aedes and Anopheles mosquitoes at the molecular level of genetics

R. Gale, K. (1986) Studies on Aedes and Anopheles mosquitoes at the molecular level of genetics. PhD thesis, University of Liverpool.

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Abstract

Section 1: Construction and screening of a genomic library for the mosquito Aedes aegypti (Diptera, culicidae). A genomic library has been constructed for this important vector of arboviral disease. Total genomic DNA and various classes of RNA from Ae. aegypti were used to screen this library. The results obtained indicate that this species has a short period interspersion pattern of repeated sequences. Transcription of these repeats could not be detected using total cytoplasmic RNA, hnRNA or mRNA as hybridisation probes. Section 2: Sequence organisation of ribosomal DNA in Aedes aegypti. The Aedes aegypti genomic library was used to isolate clones containing the intact ribosomal DNA (rDNA) repeat of this species. This has been restriction mapped and the transcribed regions have been identified. The rDNA repeat is 9.0 Kb in length and is present as approximately 500 head-to-tail tandemly repeated copies. A low level of intraspecies polymorphism of Ae. aegypti rDNA is evident. Two restriction polymorphisms have been identified within the rDNA repeat. Section 3: Analysis of ribosomal DNA variation within Ae. aegypti'and between closely related species. Four variant rDNA clones have been isolated. One of these' may contain the end of a tandem array of ribosomal genes. Another variant contains a duplication of rDNA within the internal transcribed spacer region of the ribosomal repeat. Sequence analysis of this clone has identified regions at the 3' end of the 18S rRNA gene of Ae. aegypti which show very strong homology with the corresponding regions in other species. Some repeated sequences have been identified downstream of the 18S rRNA gene in this clone. Preliminary analysis of the two other rDNA variants indicates that one contains a duplication or insertion of DNA in the 28S rRNA coding region and one contains non-transcribed spacer homologous sequences which are not associated with rRNA coding regions. Section 4: DNA probes for species identification of mosquitoes in the Anopheles gambiae complex. DNA sequences have been isolated which distinguish four of the morphologically identical members of the An. gambiae species complex. Two sequence classes were obtained. Class 1 homologues are highly reiterated in the genomes of An. arabiensis and An. merus, present in low copy number in An. melas and were not detected in An. gambiae s. s. Class 1 sequences are male specific in An. arabiensis. Class 2 homologues are highly reiterated in the genomes of An. merus and An. melas and present in low to middle copy number in An. gambiae s. s, and An. arabiensis. Sex specificity of Class 2 homologues does not occur in the species tested (An. gambiae s. s. and An. arabiensis). Hybridisation of these species specific DNA sequences to mosquitoes squashed directly onto nitrocellulose provides a simplified method of species identification.

Item Type:	Thesis (PhD)
Depositing User:	Symplectic Admin
Date Deposited:	23 Oct 2023 11:16
Last Modified:	23 Oct 2023 11:21
DOI:	10.17638/03176322
Copyright Statement:	Copyright © and Moral Rights for this thesis and any accompanying data (where applicable) are retained by the author and/or other copyright owners. A copy can be downloaded for personal non-commercial research or study, without prior permission or charge.
URI:	https://livrepository.liverpool.ac.uk/id/eprint/3176322