DOSAGE COMPENSATION OF SERINE-4 TRANSFER RNA IN DROSOPHILA MELANOGASTER

James A. Birchler ¹, R. Keith Owenby ¹, and K. Bruce Jacobson ¹

¹ The University of Tennessee-Oak Ridge Graduate School of Biomedical Sciences and Biology Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37830

A dosage series of the X chromosome site for serine-4 transfer RNA consisting of one of three copies in females and one to two in males was constructed to test whether transfer RNA expression is governed by dosage compensation. A dosage effect on the level of the serine-4 isoacceptor was observed in both females and males when the structural locus was varied. However, in males, each dose had a relatively greater expression so the normal one dose was slightly greater than the total female value and the duplicated male had the highest relative expression of all the types examined. Serine-4 levels in males and females from an isogenic Oregon-R stock were similar. Thus the transfer RNA levels conform to the expectations of dosage compensation.