Below is a diagram of a DNA replication fork in E. coli . Answer the following q

Question

Below is a diagram of a DNA replication fork in E. coli. Answer the following questions relating to the parts of the model indicated by the numbered arrows.

1. Is this the 5' or the 3' end of the chain?

2. Is this the 5' or the 3' end of the chain?

3. What is the role of this enzyme found at the replication fork?

4. What is the name of the proteins that keep the template strands separated?

5. What is the name of the enzyme that releases the supercoiling caused by strand separation?

6a. What kind of molecule is used as a primer for new DNA strands?

6b. What is the name of the enzyme that makes the primer for DNA synthesis?

7. Is the synthesis of new DNA on this strand continuous or discontinuous?

8. What are the short fragments of newly synthesized DNA called?

9. What is the name of the enzyme that seals the nicks between these fragments?

Explanation / Answer

1. Is this the 5' or the 3' end of the chain?

ANS: 3' end

2. Is this the 5' or the 3' end of the chain?

ANS: 5' end

3. What is the role of this enzyme found at the replication fork?

ANS: DNA helicase. It is an enzyme that can unwinds the DNA double helix by breaking the hydrogen bonds between the complementary bases.

4. What is the name of the proteins that keep the template strands separated?

ANS: single strand binding protein

5. What is the name of the enzyme that releases the supercoiling caused by strand separation?

ANS: Topoisomerase

6a. What kind of molecule is used as a primer for new DNA strands?

ANS: RNA molecules.

6b. What is the name of the enzyme that makes the primer for DNA synthesis?

ANS: Primase is an enzyme that synthesizes short RNA sequences (primers). The primase produces RNA molecules, the enzyme is a type of RNA polymerase.

7. Is the synthesis of new DNA on this strand continuous or discontinuous?

ANS: This strand is continuous strand.

8. What are the short fragments of newly synthesized DNA called?

ANS: Okazaki fragment (during DNA replication formed on lagging template strand)

9. What is the name of the enzyme that seals the nicks between these fragments?

ANS:DNA Ligase (During DNA replication the DNA Ligase can seals breaks or nicks together)

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