Null Activity Allele Research Articles

The alcohol dehydrogenase polymorphism in natural populations of Drosophila melanogaster: ADH activity variation restriction site polymorphism and the Adh cline.

Alcohol dehydrogenase activity has been measured in 186 iso-second chromosome lines--104 from seven Australian populations and 82 from six Chinese populations. Restriction endonuclease variation in the Adh gene region in these lines has previously been described (Jiang & Gibson, 1991). The mean ADH activity of AdhF and AdhS lines was significantly higher in the Chinese samples than in the Australian samples. In each population on both continents the mean activity of the AdhF lines is significantly higher than that of the AdhS lines. Six lines homozygous for a thermostability variant, AdhFChD (detected in four of the Chinese populations), had intermediate levels of ADH activity and protein amount. In a subset of the lines with the highest and lowest levels of ADH, there was a correlation of 0.69 between ADH activity and ADH CRM. None of the restriction site variants was consistently associated with the amount of ADH activity. Associations between BamHI (-7.2), the Adh polymorphism and ADH activity suggest that there are modifiers of ADH 5' to the gene. The deletion (0.2) at position -2.8 on the restriction map (Jiang & Gibson, 1991) was associated with increased levels of ADH activity in AdhS lines from China. Two unique insertions in the gene region were associated with low activity in AdhF lines and a null activity allele had a deletion removing most of exon 2. A single line with a duplication of a part of the Adh coding region and of the 5' regulatory section had relatively high ADH activity. Considering all the data, the main factor affecting ADH activity levels in populations is the frequency of AdhF.

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.

Aberrant splicing of a naturally occurring alcohol dehydrogenase null activity allele in Drosophila melanogaster

The DNA sequence of a naturally occurring alcohol dehydrogenase null activity allele, AdhnAC14, has eight extra nucleotides (in two groups of four) in the second intron, commencing six bases 3' from the 5' splice site. A stop codon was also found in exon 2. S1 nuclease protection experiments have shown that the insertions in intron 2 disrupt the correct splicing of intron 2. The null allele produces a transcript approximately 100 bases longer than the normal mature adult transcript, and the amount of the null allele transcript is only about 10% of the normal level.

Molecular structure of a naturally occurring alcoholdehydrogenase null activity allele inDrosophilamelanogaster

An alcohol dehydrogenase null activity allele, AdhnAH52, extracted from a natural population of Drosophila melanogaster has been cloned and sequenced. Compared with the wild-type consensus sequence, the nucleotide sequence of AdhnAH52 contains eight extra bases in intron 2, adjacent to the 5' splice site. It seems likely that the extra bases result from two structural changes, with a 10-base pair insertion at the same site as a 2-base pair deletion. The insertion includes an 8-base pair duplication of an adjoining region. This structural change alters transcription to give rise to an mRNA which is longer than normal and at 10% of the wild-type level.

Molecular structure of a naturally occurring alcoholdehydrogenase null activity allele inDrosophilamelanogaster

Molecular structure of a naturally occurring alcoholdehydrogenase null activity allele inDrosophilamelanogaster

Molecular structure of a naturally occurring alcohol dehydrogenase null activity allele inDrosophila melanogaster

Molecular structure of a naturally occurring alcohol dehydrogenase null activity allele inDrosophila melanogaster

Molecular structure of a naturally occurring alcohol dehydrogenase null activity allele inDrosophila melanogaster

Molecular structure of a naturally occurring alcohol dehydrogenase null activity allele inDrosophila melanogaster

Biochemical evidence for the existence of a null allele at the leucine aminopeptidase-2 (Lap-2) locus in the oyster Crassostrea virginica (Gmelin)

The existence of a null activity allele at the leucine aminopeptidase-2 (Lap-2) locus in the oyster Crassostrea virginica (Gmelin) was previously inferred from anomalous segregation patterns observed in offspring from pair crosses, and from the occurrence of individuals lacking Lap-2 bands on gels (presumed null homozygotes). The present research was done to determine whether leucine aminopeptidase specific activity was significantly reduced in oysters presumed from breeding experiments to be heterozygous for a Lap-2 null allele. Approximately thirty 4-month-old oysters from each of two crosses were analyzed. In each cross, LAP specific activity was significantly reduced (P < 0.001) in active/null heterozygotes, compared with full-sib oysters that were active/active heterozygotes. On average, active/null heterozygotes had 57% of the activity of the corresponding active/active heterozygotes.Key words: oysters, null allele, leucine aminopeptidase.

Transcription analysis of alcohol dehydrogenase null alleles from natural populations of Drosophila melanogaster.

Southern analysis of 19 Adh null activity alleles isolated from Tasmanian populations of Drosophila melanogaster have shown that there are no detectable insertions or deletions in an 11.8-kb region that contains the gene. Northern blot analyses of the null alleles have shown that they all produce a transcript about 100 bases longer than that produced by the normal allele and they accumulate a precursor of 1800 bases. The amount of the major transcript produced by the null alleles is about 10% of that produced by normal alleles. The molecular properties of the null alleles suggest that they share a common origin.

A block in the pentose shunt and in a purine degradation pathway interact to produce lethality in Drosophila melanogaster

Null activity alleles of the structural genes for glucose-6-phosphate dehydrogenase and xanthine dehydrogenase in Drosophila melanogaster have no or little measurable effect on the viability of mutant flies. In contrast, double mutant combinations lacking both enzyme activities result in lethality. This observation highlights a physiological interaction between metabolic pathways heretofore considered to be independent.

Alcohol dehydrogenase and sn-glycerol-3-phosphate dehydrogenase null activity alleles in natural populations of Drosophila melanogaster

Alcohol dehydrogenase (Adh) null activity alleles have been detected in each of 2 years in Australian populations of D. melanogaster at frequencies up to 3·9 per cent, but with an average of 1·3 per cent in 1983 and 0·7 per cent in 1984. In the same populations the frequency of sn-glycerol-3-phosphate dehydrogenase (Gpdh) null alleles was as high as 2·7 per cent with an average of 1·6 per cent in 1983 and 0·5 per cent in 1984. These values compare with previously reported frequencies of 0·09 per cent for Adh and 0·8 per cent for Gpdh in a North Carolina (U.S.A.) and a London (U.K.) population. Of the 12 second chromosomes bearing Adh null alleles, four were homozygous lethal, but all were viable and fertile in combination with Df(2L)64j.

A subcellular localization of the gene product of the DNase-1 locus in Drosophila melanogaster

A study was undertaken to determine the subcellular location of DNase-1, a major acid deoxyribonuclease in Drosophila melanogaster. Embryonic tissue used in these experiments was derived from a wild type strain and from a strain homozygous at the DNase-1 locus (3–61.8) for the null activity allele, DNase-1 n324. The majority of total acid DNase and DNase-1 activity is found in the small particulate fraction of tissue homogenates fractionated by differential centrifugation. The activity exhibits latency in these extracts indicating that it is membrane delimited. DNase-1 activity also co-equilibrates in sucrose density gradients with acid phosphatase activity which, in D. melanogaster, is known to be lysosomal. These results suggest that DNase-1 is localized largely within the lysosomes of embryonic tissue. Functional implications of a lysosomal location for DNase-1 are discussed.