Masters Theses

Date of Award

8-2001

Degree Type

Thesis

Degree Name

Master of Science

Major

Biochemistry and Cellular and Molecular Biology

Major Professor

Bruce D. McKee

Committee Members

Handle, Ganguly

Abstract

In the past fifty years many advances in understanding the mechanisms and proteins involved in recombination, the synaptonemal complex, sister chromatid cohesion, and the kinetochore have been made. Nevertheless, the longstanding fundamental question, "What are the physical forces responsible for the attraction and subsequent interactions of homologous chromosomes?," still remains unanswered. (Giroux 1988). How homologous chromosomes in the achiasmatic Drosophila melanogaster male pair and are held together was explored in this study by examining a cis-acting factor and a candidate trans-acting factor. The rDNA in Drosophila melanogaster is located on the X and Y chromosomes. Data has shown that the transcription of the cis-acting 240 bp repeats within the rDNA intergenic spacer is essential for X-Y pairing. Transcription being necessary for pairing suggests a direct role of the 240 bp RNA in pairing. The cytological location of the 240 bp repeat RNAs was examined using in situ hybridization to the RNAs in testes tissue. Staining, indicating presence of the 240 bp repeat RNAs, was observed in prophase and prometaphase in primary spermatocytes. Direct interactions of the 240bp repeats were examined using in vitro and in vivo assays. Interactions between in vitro transcribed 240bp RNAs were not observed, but peripherally produced 240 bp repeat RNAs (not transcribed from the X or Y chromosomes) did interfere with proper pairing and disjunction in vitro in males. This data points to a direct role of240 bp repeat RNAs in X-Y homolog pairing in male Drosophila meiosis. The cabeza and TLS proteins are 56% identical and share common motifs. Since TLS seems to play a role in mouse meiosis, the Drosophila homolog cabeza may play a role in fly meiosis. Two different mutant alleles of the candidate trans-acting factor cabeza were used in this study to characterize its role in meiosis. Meiosis in the cabeza mutants was characterized by looking at live and stained preparations of testis tissue. Meiosis appeared normal in live and stained preparations of testes tissues for both mutants. It appears that the cabeza protein is not essential for Drosophila male meiosis.

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