Biomedical subjects

R G Rowan

Publications and source records attributed to R G Rowan.

8 recordsLinked to original sources

PubMed1991

Rates of DNA change and phylogeny from the DNA sequences of the alcohol dehydrogenase gene for five closely related species of Hawaiian Drosophila.

The sequence of 1.6 kb of DNA surrounding the alcohol dehydrogenase (Adh) gene from five species of the Planitibia subgroup of the Hawaiian picture-winged Drosophila, with estimated divergence times of 0.4-5.1 Myr, has been determined. The gene trees which were found by using the sequence divergence from different regions of the sequences are generally in accord with the phylogeny proposed for these species when chromosomal inversions and island of origin are used. One of the species (D. picticornis) appears to be more distant from the other species in this group than they are from a member of the Grimshawi group (D. affinidisjuncta) which is chromosomally more distant. Two of the species (D. differens and D. plantibia) show heterogeneity in the nucleotide changes in the Adh coding region, heterogeneity which is interpreted to be due to a gene conversion or recombination after hybridization between the two species. The minimal rate of nucleotide substitution of synonymous nucleotides and of nontranscribed nucleotides downstream from the coding region is estimated as 1.5 x 10(-8) and 1.1 x 10(-8) substitutions/nucleotide/year, respectively. This rate is two to three times the maximal rate estimated for mammalian synonymous substitutions.

Alcohol Dehydrogenase↗

PubMed1986

Developmentally regulated RNA transcripts coding for alcohol dehydrogenase in Drosophila affinidisjuncta.

The organization of the gene coding for alcohol dehydrogenase (Adh) in Drosophila affinidisjuncta has been determined by physically mapping Adh RNA transcripts to cloned genomic DNA. Two distinct transcript types accumulate with developmental specificity. Because only a single genomic Adh locus is detected in D. affinidisjuncta, and since all Adh transcripts appear to be identical except at their termini, the two Adh RNA types are products of the same gene. One type of transcript, abundant in adults, contains a small 5' terminal exon that is completely lacking in the other type of transcript, which accumulates in larvae. This 5' end difference suggests that the D. affinidisjuncta Adh gene, like the homologous gene from the distantly related species D. melanogaster, is expressed from two promoters. According to the transcription map, these D. affinidisjuncta promoters are separated by approximately 560 base pairs of genomic DNA sequence. D. affinidisjuncta Adh transcripts also resemble D. melanogaster Adh transcripts in both their overall organization and their developmental distribution. Multiple 3' ends are responsible for the size heterogeneity of both types of D. affinidisjuncta Adh RNA, and some of these also appear with stage specificity.

Alcohol Dehydrogenase↗

PubMed1986

Two alternative transcripts coding for alcohol dehydrogenase accumulate with different developmental specificities in different species of picture-winged Drosophila.

Two alternate transcripts of the single copy Alcohol dehydrogenase (Adh) gene accumulate with developmental specificity in all of 12 species of Hawaiian picture-winged Drosophila which have been examined. Relative to the paradigm species D. affinidisjuncta, the Adh transcript normally restricted to larvae is found to accumulate in both larval and adult tissues in D. formella. The other Adh transcript, which normally accumulates only in adults, accumulates in third-instar D. prostopalpis larvae as well. In species hybrids, the D. formella phenotype shows additive inheritance. These observations document the existence of a novel type of genetic variability. Furthermore, such variants suggest specific properties for the biological systems that regulate ADH expression in Drosophila, and they should facilitate further experimental investigations.

Alcohol Dehydrogenase↗

PubMed1984

Introduction of a functional P element into the germ-line of Drosophila hawaiiensis.

When a plasmid carrying a P-transposable element (derived from Drosophila melanogaster) is injected into young embryos of D. hawaiiensis, the P-element sequence from the plasmid transposes into the germ-line chromosomes. The introduction of this P element into D. hawaiiensis provides an opportunity to study the behavior of the transposable element in a novel context. Germ-line transposition and numerical increase of the P elements are readily detected in D. hawaiiensis. Thus these aspects of P-element function do not require chromosomal or cytoplasmic properties that are unique to D. melanogaster. Since D. hawaiiensis is among those Drosophila that are most distantly related to D. melanogaster, these results suggest that P-element-mediated transformation may function in many species.

Animals↗

PubMed1984

Regulatory gene evolution: adaptive differences in expression of alcohol dehydrogenase in Drosophila melanogaster and Drosophila simulans.

In Drosophila melanogaster X D. simulans hybrids, the alcohol dehydrogenase (ADH) electromorphs characteristic of the two parents display tissue- and stage-specific differences in relative level of expression. This implies distinct cis-acting regulatory elements associated with the respective Adh alleles. These cis-acting elements account in part, but not completely, for markedly different overall patterns of ADH expression in the two species. The regulatory patterns seem to be adaptively significant since they correlate with species-specific patterns of ethanol tolerance. The activity differences are accounted for by different levels of enzyme protein, but the underlying mechanisms have not been fully analysed and may be complex. Independent evolution of various aspects of the ADH developmental programme may relate to use of different promoters for transcription of the Adh locus in different developmental contexts. This system illustrates the potential importance of regulatory genes in evolution and provides a model for investigating the molecular basis of evolved regulatory differences.

Alcohol Dehydrogenase↗

PubMed1984

Isolation and initial characterization of the alcohol dehydrogenase gene from Drosophila affinidisjuncta.

Recombinant bacteriophages containing the alcohol dehydrogenase (ADH) gene from Drosophila affinidisjuncta have been isolated by virtue of their cross-hybridization to the previously cloned ADH gene from D. melanogaster. Within the 17 kilobases of cloned DNA represented in the phage genomes, the sequences hybridizing to the D. melanogaster ADH gene lie roughly in the center. The only region of detectable hybridization to cDNA made from templates of D. affinidisjuncta larval poly(A)-containing RNA maps to the same portion of the cloned DNA. Verification that the phages carry the ADH structural gene was obtained by hybrid-selecting ADH mRNA, translating it in vitro, and immunoprecipitating the resulting ADH polypeptide. Analysis of genomic DNA suggests that the ADH gene and most flanking sequences are present only once in the haploid genome. However, 3' to the ADH gene, two separable repetitive elements are found. Both repetitive elements are probably small and poorly conserved in the genome, and neither interferes with localization of the ADH gene, by in situ hybridization, to a position near the base of the third chromosome. Analysis of ADH transcripts demonstrates that there are at least four RNAs produced by the ADH gene. Two size classes of RNA are seen at each stage of development. In addition, ADH transcripts from larvae and adults differ from one another in a reproducible manner.

Alcohol Dehydrogenase↗

PubMed1981

Characterization of plasmids in Erwinia stewartii.

Plasmids in 39 strains of Erwinia stewartii were examined by agarose gel electrophoresis. Most virulent strains had from 11 to 13 plasmids ranging in molecular mass from 2.8 to 210 megadaltons and contained plasmids of 210, 70, 49, 43, 29.5, 16.8, 8.8, and 2.8 megadaltons. Plasmids in strains SW2 and SS104 were characterized by both electron microscopy and agarose gel electrophoresis and may be useful as convenient references for sizing plasmids by electrophoresis. Specific size classes of plasmids could not be associated with antibiotic and heavy metal resistance, carbohydrate utilization, bacteriocin production, or pathogenicity to corn. However, avirulent strains tended to have fewer plasmids than virulent strains.

DNA↗

PubMedDate not supplied

Nucleotide sequence of the genomic region encoding alcohol dehydrogenase in Drosophila affinidisjuncta.

The DNA sequence of a 3886-bp genomic region containing the alcohol dehydrogenase (Adh) gene from Drosophila affinidisjuncta, and the RNA sequences of the D. affinidisjuncta Adh transcripts, are presented. These data support the conclusion that two Adh promoters generate distinct, developmentally regulated Adh transcripts. Correlations between these sequences and the transcription map are discussed. Comparisons between these and equivalent data from D. melanogaster are also presented. We note the following observations: (1) Except at the extreme 3' end, the two genes are identically organized. (2) Drosophila Adh protein accumulates amino acid replacements at the rate of approximately 0.5 per million years. (3) Among the non-protein-coding DNA sequences, putative homologies occur in the two promoter regions.

Alcohol Dehydrogenase↗