Date of Award
2-1988
Document Type
Dissertation - Restricted
Degree Name
Doctor of Philosophy (PhD)
Department
Biological Sciences
First Advisor
James B. Courtright
Second Advisor
Stephen Munroe
Third Advisor
Walter Fredricks
Fourth Advisor
Dale Noel
Fifth Advisor
A. Krishnakumaran
Abstract
The aim of this study was to identify and compare regions of nucleotide sequence homology between similar genes that are abundantly expressed and maternally transmitted during Drosophila oogenesis. To identify such genes, a Drosophila egg chamber cDNA library was differentially screened such that maternal RNA sequences were readily identified and selected from the recombinant population. Genomic and cDNA clones complementary to an abundant maternal mRNA were isolated and analyzed with regard to molecular structure, genomic location, transcript expression, and putative gene function. The gene codes for a 650 nt transcript which is expressed in greater abundance in ovaries, embryos, and third instar larvae relative to other tissues and developmental stages. Southern blot analysis indicated that this gene shared limited nucleotide similarity with several other Drosophila genomic sequences. In situ hybridization to polytene chromosomes localized this gene within the Minute region M(2)21C1-2, on chromosome 2L. Computer analysis of the DNA sequence of the 21C cDNA revealed a 76 percent 3$\sp\prime$ coding sequence similarity with the Drosophila acidic ribosomal protein gene, A1 (Qian et al., 1987). The deduced protein product is 113 amino acids in length and contains a sequential stretch of hydrophobic and hydrophilic residues at the carboxyl terminus. This portion of the protein is rich in glutamic and lysine residues and is highly conserved among several species examined. These conserved structural features classify 21C as a member of the "A" type ribosomal proteins; ones which are proposed to involved in the binding of initiation, elongation and termination factors of protein synthesis. Additionally, five representative, cross hybridizing genomic clones were isolated based upon 3$\sp\prime$ nucleotide similarity with 21C cDNA sequences. Each genomic clone hybridized in situ to a different Minute locus. One clone hybridized to the Minute locus 5E, a region containing the gene for acidic ribosomal protein 7/8 (Burns et al., 1984). These results suggest that the 3$\sp\prime$ sequences common to the genomic clones define a subset of Drosophila ribosomal proteins that share similar functional residues.