Topľa

Topľa (Hungarian: Tapoly, German: Töpl) is a river in eastern Slovakia and right tributary of Ondava. It is 129.8 km long and its basin covers an area of 1,503 km². It rises in the Čergov mountains, flows through Ondava Highlands, Beskidian Piedmont, Eastern Slovak Hills and Eastern Slovak Flat and flows into Ondava in the cadastral area of Parchovany. It flows through towns of Bardejov, Giraltovce, Hanušovce nad Topľou and Vranov nad Topľou.

Coordinates: 48°44′N 21°45′E / 48.733°N 21.750°E / 48.733; 21.750

TOP2A

DNA topoisomerase 2-alpha is an enzyme that in humans is encoded by the TOP2A gene.

This gene encodes a DNA topoisomerase, an enzyme that controls and alters the topologic states of DNA during transcription. This nuclear enzyme is involved in processes such as chromosome condensation, chromatid separation, and the relief of torsional stress that occurs during DNA transcription and replication. It catalyzes the transient breaking and rejoining of two strands of duplex DNA which allows the strands to pass through one another, thus altering the topology of DNA. Two forms of this enzyme exist as likely products of a gene duplication event. The gene encoding this form, alpha, is localized to chromosome 17 and the beta gene is localized to chromosome 3. The gene encoding this enzyme functions as the target for several anticancer agents and a variety of mutations in this gene have been associated with the development of drug resistance. Reduced activity of this enzyme may also play a role in ataxia-telangiectasia.

TOP3A

DNA topoisomerase 3-alpha is an enzyme that in humans is encoded by the TOP3A gene.

Function

This gene encodes a DNA topoisomerase, an enzyme that controls and alters the topologic states of DNA during transcription. This enzyme catalyzes the transient breaking and rejoining of a single strand of DNA which allows the strands to pass through one another, thus reducing the number of supercoils and altering the topology of DNA. This enzyme forms a complex with BLM which functions in the regulation of recombination in somatic cells.

Meiosis

Recombination during meiosis is often initiated by a DNA double-strand break (DSB). During recombination, sections of DNA at the 5' ends of the break are cut away in a process called resection. In the strand invasion step that follows, an overhanging 3' end of the broken DNA molecule then "invades" the DNA of an homologous chromosome that is not broken forming a displacement loop (D-loop). After strand invasion, the further sequence of events may follow either of two main pathways leading to a crossover (CO) or a non-crossover (NCO) recombinant (see Genetic recombination and see Figure). The pathway leading to a NCO is referred to as Synthesis-dependent strand annealing (SDSA).