MUTATIONAL MECHANISMS, PHYLOGENY, AND EVOLUTION OF A REPETITIVE REGION WITHIN A CLOCK GENE OF DROSOPHILA-MELANOGASTER

The D. melanogaster clock gene period (per) is an internally repetitiv e gene encoding a tandem array of Thr-Gly codons that are highly polym orphic in length in European natural populations. The two major length variants, (Thr-Gly)(20) and (Thr-Gly)(17), show a highly significant latitudinal dine. In this study we present the complete sequence of th e Thr-Gly region of 91 individuals from 6 natural populations of D. me lanogas ter, 5 from Europe and 1 from North Africa. We further charact erized these 91 individuals for polymorphic sites in two other regions , one upstream and one downstream of the Thr-Gly repeat, We used the h aplotypic combinations of Thr-Gly allele with flanking markers in an a ttempt to identify the mechanisms involved in the evolution of the D. melanogaster Thr-Gly region and to infer the phylogenetic relationship existing among the Thr-Gly alleles. We observe evidence for both intr a- and interallelic mutational mechanisms, including replication slipp age, unequal crossing-over, and gene conversion.