Lucinda M.C. Hall

The Ace locus of Drosophila melanogaster: structural gene for acetylcholinesterase with an unusual 5' leader

The Ace locus of Drosophila melanogaster has been mapped at the molecular level. cDNA clones from the locus have been isolated and their sequence determined, confirming that Ace forms the structural gene for acetylcholinesterase (AChE). The cDNAs have a 1950 nucleotide open reading frame from which the complete amino acid sequence of AChE has been deduced. The Drosophila enzyme is found to have extensive homology to the known sequence of Torpedo AChE. Ace cDNAs have an unusual structure with a long 5′ leader and several short upstream open reading frames.

The expression of heat shock genes during normal development in Drosophila melanogaster (heat shock/abundant transcripts/developmental regulation)

SummaryDrosophila melanogaster cells and tissues respond to heat shock by dramatically altering their pattern of transcription and translation, leading to the rapid synthesis of a small number of polypeptides, the heat shock proteins (hsps). By using cloned hsp DNA we have detected sequences complementary to heat shock genes in RNA prepared from non-heat-shocked animals of different developmental stages. Hsp 83 mRNA is present at high levels in all stages examined. Hsp 68 and 70 mRNAs are present at very low levels in most stages and at slightly higher concentration in pupae. Hsp 26 and 27 mRNAs are detected in embryos. Hsp 23, 26 and 27 mRNA are barely detectable in early third instar larvae but are major components of late third instar and early pupal RNA. Hsp 22 mRNA is also detected in early pupae. Later in development the levels of the small hsp mRNAs decrease but a further peak in abundance of hsp 26 and 27 mRNAs is found in mature adult females.

Genetic activity along 315 kb of the Drosophila chromosome

Transcripts from different tissues were mapped along a 315 kb segment of the Drosophila chromosome, a region which includes the rosy and Ace loci. Forty‐three distinct RNA species were detected, though only 12 recessive lethal complementation groups had been mapped in the interval. The sum of the sizes of the transcripts covers 33% of the genomic DNA. The distribution of transcription units along the walk is very uneven. Sixty‐three kb of genomic DNA at the proximal end of the walk encode 18 transcripts, while only seven are found in the next 153 kb. Each tissue exhibits a specific spectrum of transcripts. No clustering was seen among genes expressed coordinately. In salivary glands, the number of transcripts detected corresponds to the number of chromomeric units in the polytene chromosomes of this tissue. Moreover, the density distribution of transcripts along the DNA walk is parallel to the density distribution of chromomeric units.

Transcripts, genes and bands in 315,000 base-pairs of Drosophila DNA

We have mapped transcripts arising from 315,000 base-pairs of DNA from chromosome region 87D,E of Drosophila melanogaster. The DNA is represented in a series of overlapping recombinant phages; it constitutes about 14 bands in the polytene chromosome from 87D5,6 to 87E5,6 and contains the essential sequences for at least 12 complementation groups. We have defined 20 discrete polyadenylated RNA species transcribed from non-repetitive DNA in the region at various developmental stages. There is a generally good correlation between the position of transcription units, chromomeric units and complementation groups but with some significant exceptions. In particular, the two large bands in the region (E1,2 and E5,6) each contain several transcription units. We also find that a major part of a large band (E1,2) has no detectable transcripts and is apparently genetically silent.

Modifiers of position-effect variegation in the region from 86C to 88B of the Drosophila melanogaster third chromosome

SummaryFour dominant suppressor and one enhancer of variegation loci were mapped in the polytene chromosome region extending from section 86C to section 88B of the Drosophila melanogaster third chromosome using a set of deficiencies. The suppressor locus Su-var(3) 14 maps in 86CD, Su-var(3) 13 in 86F4-7, Su-var(3)6 in 87B4-7 and Su-var(3)7 in 87E4-5. The enhancer locus E-var(3)3 maps in 87E12-F11. Su-var(3)13, Su-var(3)6 and Su-var(3)7 are also defined by point mutant alleles originally identified by other criteria (Reuter et al. 1986). Duplications covering the suppressor loci Su-var(3)14, Su-var(3)13, Su-var(3)6 and Su-var(3)7 were found to reduce considerably the haplo-abnormal effect of heterozygous point mutants of the corresponding loci. One suppressor locus, Su-var(3)7, maps within a region which has previously been cloned. The positions of deficiency breakpoints delimiting the suppressor locus indicate that all the necessary sequences for its function are located within 10 kb of cloned DNA.