Restriction map variation at the adh locus of Drosophila melanogaster in inverted and noninverted chromosomes.

Restriction map variation among 39 Standard and 40 In(2L)t chromosomes extracted from a Spanish natural population of Drosophila melanogaster was investigated for a 2.7-kb region encompassing the Adh locus with ten four-cutter restriction enzymes. A total of 20 polymorphisms were detected, representing 15 restriction site polymorphisms, 4 length polymorphisms and the allozyme polymorphism. Variation at the DNA level was compared among St-Adh(F), St-Adh(S) and t-Adh(S) chromosomes. t-Adh(S) chromosomes show a higher level of variation than St-Adh(F) chromosomes. This suggests that In(2L)t arose before the fast/slow allozyme divergence in the evolutionary history of D. melanogaster.