DNA Replication and Topoisomerase Functions

The video tutorial explains the process of DNA unwinding during replication, likening it to pulling apart a rope, which builds up twisting tension. To manage this tension, DNA can form supercoils. The video discusses two methods to release this tension: cutting one or both strands of DNA. Topoisomerase 1 cuts a single strand, allowing the other to pass through and resealing it, reducing tension by one twist. Topoisomerase 2 cuts both strands, passing another double strand through the break, and resealing it, effectively removing supercoiling two twists at a time.

What happens to the DNA strands as they are pulled apart during replication?

• They form new strands immediately.

• They break apart completely.

• They build up twisting tension.

• They become more relaxed.

What is the result of relaxing tension on a supercoiled DNA?

• The DNA becomes more tightly coiled.

• The DNA strands break.

• The DNA strands separate completely.

• The DNA forms a relaxed circle.

Which enzyme cuts a single strand of the DNA double helix to relieve tension?

• Ligase

• Topoisomerase 1

• Helicase

• Topoisomerase 2

How does Topoisomerase 2 differ from Topoisomerase 1 in its function?

• It cuts only one strand of DNA.

• It adds twists to the DNA.

• It cuts both strands of DNA.

• It does not reseal the DNA.

What is the primary function of topoisomerase enzymes during DNA replication?

• To synthesize new DNA strands.

• To add more twists to the DNA.

• To unwind the DNA strands completely.

• To relieve tension by cutting and resealing DNA strands.

What happens when a DNA molecule is supercoiled?

• It breaks into smaller pieces.

• It forms new DNA strands.

• It cannot be separated further without intervention.

• It becomes more stable.