MOLECULAR RELATIONSHIPS BETWEEN ALCOHOL-DEHYDROGENASE NULL-ACTIVITY ALLELES FROM NATURAL-POPULATIONS OF DROSOPHILA-MELANOGASTER

Alcohol dehydrogenase null-activity alleles extracted from a number of natural populations of Drosophila melanogaster in Tasmania were shown to be molecularly similar by probing, with an oligonucleotide specific to an inserted region in intron 2 of the gene, genomic DNA amplified by the polymerase chain reaction. This insertion had previously been shown to be the cause of the loss of activity in one of the null alleles whose DNA sequence was known. Three Adh null alleles from mainland populations did not contain the insertion. Two of these null alleles, extracted from the Coffs Harbour population in different years, were cloned, and their DNA sequences showed that they were identical and that both had a 438-bp deletion which removed most of exon 2. The third null allele, identified in a sample of flies from Chateau Tahbilk, was shown by 4-bp restriction-endonuclease mapping to contain a 320-bp insertion in intron 1, although this may not be the cause of the loss of activity. The data show that at least three different Adh null alleles have been found in Australian populations and that at least two have been maintained as heterozygotes over a period of years.