AP BIOLOGY

Detailed explanation-1: -The enzyme DNA helicase works with topoisomerase during DNA replication. Whereas topoisomerase functions to relieve the pressure during the uncoiling of DNA, helicase works to physically separate the strands of double-stranded DNA from each other.

Detailed explanation-2: - DNA topoisomerases are ubiquitous enzymes found in all cell types from viruses to man. These enzymes act to regulate DNA supercoiling by catalysing the winding and unwinding of DNA strands.

Detailed explanation-3: -During DNA replication, DNA helicases unwind DNA at positions called origins where synthesis will be initiated. DNA helicase continues to unwind the DNA forming a structure called the replication fork, which is named for the forked appearance of the two strands of DNA as they are unzipped apart.

Detailed explanation-4: -Of all the enzymes required to sustain cellular growth, topoisomerase II is one of the most dangerous (4–8). As discussed below, this enzyme unwinds, unknots and untangles the genetic material by generating transient double-stranded breaks in DNA (8–12).