Scientists discovered a fossilized cockroach trapped in amber, which was supposed to be about 50 million years old. DNA fingerpr
inting and comparison with today’s living cockroaches revealed that modern cockroaches have certain additional genes which allow them to survive in today’s colder climate. Which of these could be the correct explanation for this discovery?
2 answers:
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Answer: The tension is relieved by an enzyme named topoisomerase
Explanation:
As replication starts DNA polymerase needs to move forward of double strand DNA, this creates a lot of tension in the DNA molecule. The tension is relieved by the action of an enzyme named topoisomerase. The stress relieve is needed for the progresion of the replication mechanism.
There are to types of topoisomerases:
a) Topoisomerase I
b) Topoisomerase II
Topoisomerase I underwinds the DNA double helix by making a single cut in one of the strands of the DNA molecule. Once the cut is made, the DNA unwinds and torsional stress is released. Finally the DNA strand , that was cut is ligated ( see attached image)
Topoisomerase II acts when torsional stress is made because two DNA strands cross each other (superhelical stress). Topoisomerase II cuts both strands of a DNA molecule. After this cut is made the DNA unwinds and torsiona stress is relieved ). Finally both DNA strands are ligated ) see attached image)
Topoisomerases II enzymes require ATP hydrolysis to perform the cut of both of the DNA strands.
