Structure and Evolution of the Genome of Musca Domestica (Housefly) with Comparisons to Other Dipteran Species

Abstract

This study investigates the genomic organisation of Musca domestica, Drosophila melanogaster, and Drosophila hydei. Evidence is presented, based on isolation of repetitive elements from limited genomic libraries, confirming the presence of a form of short period interspersion in the M. domestica genome and long period interspersion in the Drosophila genomes. The pattern exhibited by the housefly genome is very different from the long period interspersion shown by most insect species but is distinct from the short period interspersion found in mammals, with longer repetitive sequences, on average, than other short period interspersed genomes described. At least six families of moderately repetitive elements have been found in the housefly genome in relatively high copy number (1000's of copies per haploid genome) and an unknown number of lower copy number families. No high copy number repetitive elements have been found in the D. melanogaster genome (Dowsett 1983), which is characterised by low copy number repetitive elements. The D.Hydei genome contains at least one family of repetitive elements present in relatively high copy number (van der Veen & Dowsett in preparation). Low copy number moderately repetitive elements have not been found in any other short period interspersed genome. This infers a correlation between the pattern of interspersion and the number of high copy number moderately repetitive elements in a genome. These results lead to the proposal that a set of sequences in a long period interspersed housefly ancestor may have amplified and reinserted into the genome thereby converting the genomic organisation to short period interspersion. Amplification events may occur often in evolutionary terms meaning that genomic architecture may not be a good measure of species relatedness. A paper, entit led ‘The genome of the Housefly (Musca domestica ) is characterised by a variant form of short period interspersion’ has been submitted for publication based on the results of this investigation. Sequence information was obtained from representitives of three of the housefly families identified. The sequence information induces speculation regarding the nature and evolutionary origins of these Mused domestica repetitive elements.