Organization And Evolution Of The Alcohol Dehydrogenase Gene In Drosophila (molecular Clock, Dna Sequence Analysis, Polymorphism, Simulans And Mauritiana, Speciation).

The alcohol dehydrogenase gene of Drosophila has been studied extensively by a variety of genetic and biochemical means. Because it has been so well-characterized, it can be used as a model to make generalizations which may extend to other eukaryotic gene-enzyme systems. In this study, the Adh gene was isolated from genomic (lamda) clone libraries of D. simulans and D. mauritiana, and the DNA sequence of a 4.6 kb region containing the gene and flanking sequences was determined. The DNA sequence in each of these species was compared with that determined by others in D. melanogaster, which has been previously examined in detail, in order to identify conserved features of gene organization and to assess the types of changes which occur in the Drosophila genome during evolution. Based on this DNA sequence comparison, it is apparent that D. simulans and D. mauritiana Adh share structural features found in D. melanogaster Adh, including two promoters for the single Adh gene, which are used differentially to control Adh expression at various developmental stages. Regulation of Adh expression has been examined by others using transformation of mutagenized D. melanogaster Adh-containing DNA fragments. Integration of information generated here by interspecies DNA sequence comparisons, in regions suggested to be regulatory by the transformation method, identified several regions 5' to the promoters as possible regulatory elements. Analysis of a highly conserved region 3' to the Adh gene suggests that a previously unidentified gene lies immediately adjacent to Adh and is transcribed in the same orientation. Inter- and intra-species DNA comparisons of the Adh gene and flanking regions reveal some differences in the types of DNA changes which seem to be correlated with the processes of speciation and polymorphism. Intraspecies comparisons show many fewer amino acid replacements and much smaller length variation than exist between species. Finally, divergence of DNA in and around the Adh gene has been used to assess species and allelic relationships and to estimate times of divergence. In this initial study of closely-related species, the pattern of evolutionary divergence of Adh appears to support the concept of a DNA molecular clock.Ph.D.Biological SciencesMolecular biologyUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/127749/2/8520884.pd