Masters Theses

Weitao Sun

Date of Award

8-1996

Degree Type

Thesis

Degree Name

Master of Science

Major

Life Sciences

Major Professor

Bruce D. McKee

Committee Members

Mary Ann Handel, Ranjan Ganguly

Abstract

In Drosophila melanogaster males, sex chromosome pairing during meiosis is mediated by rRNA genes which are located in the heterochromatin of the X chromosome. Analysis of constructed rDNA fragments showed that promoter-containing rDNA fragments are autonomously capable of being transcribed and of functioning as X-Y pairing sites. Pairing ability is proportional to the dose of 240bp intergenic spacer (IGS) repeats. Each of these repeats contains a functional rDNA promoter. In this study, we made point mutations within the promoter of the 240bp IGS repeat, ligated multiple repeats containing these mutations head-to-tail and then introduced a resulting mutant oligomer onto an rDNA- deficient X chromosome by P-element mediated transformation. The effects of these transgene insertions on the frequency of X-Y pairing and disjunction were analyzed both by cytological and genetic experiments. The failure of these sequences to mediate X-Y pairing and normal disjunction bears on the importance of transcriptional activity for the pairing function of ribosomal repeats.

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