Assertion: The coling tension created by the helicase is removed by the Topoisomerase enzyme which is also called DNA gyrase in prokaryotes.

Reason: DNA polymerase II adds nucleotides only in one direction which is 3'-5'.

Explanation:

Helicase: Helicase is an enzyme responsible for unwinding the double-stranded DNA during DNA replication. It breaks the hydrogen bonds between the complementary nucleotides, separating the DNA strands and creating a replication fork.

Topoisomerase: Topoisomerase is an enzyme that helps to relieve the torsional strain or supercoiling ahead of the replication fork caused by the unwinding of DNA by helicase. In prokaryotes, the topoisomerase enzyme is also called DNA gyrase.

Role of Topoisomerase:
1. Relieving Torsional Strain: As the helicase unwinds the double-stranded DNA, it creates tension or torsional strain ahead of the replication fork. This strain can impede the progress of the replication machinery. DNA gyrase, or topoisomerase II, is responsible for relieving this tension by introducing negative supercoiling ahead of the replication fork. It does this by cutting both strands of the DNA, passing another portion of the DNA through the break, and then resealing the break. This process helps to reduce the torsional stress and allows the replication fork to proceed.

Role of DNA Polymerase II:
1. Directionality: DNA polymerase II is an enzyme involved in DNA replication. It adds nucleotides to the growing DNA strand in a 5' to 3' direction. This means that it can only add nucleotides to the 3' end of the existing DNA strand.

Conclusion:
The assertion is correct. The tension created by the helicase during DNA replication is indeed removed by the topoisomerase enzyme, also known as DNA gyrase in prokaryotes. The reason given in the statement, that DNA polymerase II adds nucleotides in the 3'-5' direction, is not directly relevant to the role of topoisomerase in relieving the tension. The directionality of DNA polymerase II is important for proper DNA replication, but it is not directly involved in the removal of tension caused by helicase.