Abstract
Homologous pairing refers to the physical alignment of homologous chromosomes. This alignment is a key feature of meiosis and is seen in nonmeotic cells of several organisms, most notably in Drosophila. A number of intriguing biological events center around homologous pairing; however, the dynamics of homologous pairing remains a mystery. Transvection is one biological event observed in Drosophila that depends on the pairing of homologous chromosomes. Transvection is the process of an allele from one chromosome interacting in trans with its corresponding allele on the other chromosome, which usually leads to intragenic complementation. This phenomenon is exhibited by a few loci in Drosophila and acts as an excellent assay for the pairing of homologs. Topoisomerase II, an enzyme that generates double-strand breaks and plays a role in chromosome structure, has been suggested to play an important role in homolog pairing. To test if Topoisomerase II is important for pairing of homologs, I blocked its function with ICRF-193 and teniposide (VM-26), two agents known to inhibit Topoisomerase II in different ways. ICRF-193 disrupts transvection at the vg, Cbx, Ubx, dpp, andlz loci, while VM-26 did not disrupt transvection. This disruption of transvection gives further evidence that Topoisomerase II plays a role in the pairing of homo logs.