In the present study Drosophila melanogaster was used to define the organization and expression of tRNA genes. The three major Drosophila valine tRNAs were isolated and purified
by standard chromatographic techniques. Nucleoside
analysis indicated that of these tRNAs only tRNA₄Val contained
inosine. All three tRNAsVal contained ribothymidine, therefore they resemble yeast tRNAVal in this regard but not the mammalian tRNAsVal
which lack ribothymidine.
The purified tRNAs were labelled with ¹ ² ⁵I and used to
determine the location of the genes for these tRNAs utilizing
the technique of in situ hybridization to salivary gland
chromosomes. tRNA₄Val
hybridized consistently to one site
on the right arm of the second chromosome, 56D, which is close
to the site of 5S RNA, 56F. tRNA₃bVal
hybridized to two sites,
84D and 92B, both on the right arm of the third chromosome.
The labelling of site 84D was approximately twice as heavy
as that of 92B. Dr. A. Delaney (unpublished) has shown that
approximately 13 genes code for tRNA₃bVal per haploid genome.
The in situ hybridization data suggests that the 13 genes
are divided such that approximately 8 genes are at site 84D
and 5 genes are at site 92B.
Evidence to support this supposition is derived from
measurements on the amount of tRNA₃bVal in mutant flies deficient
or duplicated for site 84D on one of their two homologous
third chromosomes. tRNA₃bVal amounts, measured relative to the
other tRNAVal isoacceptors decrease 31% in the deficiency
and increase 30% in the duplication. These results demon-
strate a direct relationship of the amount of tRNA₃bVal to
gene dosage because the duplication has 8 extra genes, which
is a 30% increase and the deletion has 8 fewer genes, a 30%
decrease. Finally, it was shown that the amount of total tRNSVal increased by 17% in the duplication but did not decrease
in the deletion. This result demonstrates the amount of valine tRNA is under a type of control in which the amount of total valine tRNA is increased to compensate for the deficiency
of a single isoacceptor. Also the coding properties of four tRNASer isoacceptors were determined. / Medicine, Faculty of / Biochemistry and Molecular Biology, Department of / Graduate
| Identifer | oai:union.ndltd.org:UBC/oai:circle.library.ubc.ca:2429/20544 |
| Date | January 1977 |
| Creators | Dunn, Robert James |
| Source Sets | University of British Columbia |
| Language | English |
| Detected Language | English |
| Type | Text, Thesis/Dissertation |
| Rights | For non-commercial purposes only, such as research, private study and education. Additional conditions apply, see Terms of Use https://open.library.ubc.ca/terms_of_use. |
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