Exploring DNA Replication: Leading vs Lagging Strand Dynamics

The video tutorial explains DNA replication, highlighting its semi-conservative nature, where each new DNA molecule retains one original strand. It covers the anti-parallel and complementary nature of DNA strands, the role of hydrogen bonds, and the function of enzymes like helicase, gyrase, and polymerase. The video also discusses the continuous synthesis of the leading strand and the discontinuous synthesis of the lagging strand, forming Okazaki fragments. It concludes with the proofreading and repair functions of DNA polymerases and includes practice problems for review.

What does it mean when DNA replication is described as semi-conservative?

• Each new DNA molecule contains two old strands.

• Each new DNA molecule contains one old strand and one new strand.

• Each new DNA molecule contains a mix of old and new segments.

• Each new DNA molecule contains two new strands.

In which direction do the two DNA strands run relative to each other?

• Random

• Parallel

• Perpendicular

• Anti-parallel

Which base pairs with adenine in DNA?

• Uracil

• Guanine

• Thymine

• Cytosine

How many hydrogen bonds are there between guanine and cytosine?

• One

• Four

• Three

• Two

What is the role of helicase in DNA replication?

• Seals the nicks between Okazaki fragments

• Separates the two DNA strands

• Adds nucleotides to the new strand

• Synthesizes RNA primer

Which enzyme relieves torsional strain ahead of the replication fork?

• Helicase

• Primase

• Topoisomerase

• DNA ligase

What is the function of single-stranded binding proteins (SSB proteins)?

• They synthesize the RNA primer.

• They add nucleotides to the new strand.

• They protect and stabilize the separated DNA strands.

• They seal the nicks between Okazaki fragments.

In which direction does DNA polymerase III add nucleotides?

• 3' to 5'

• 5' to 3'

• Randomly

• Both directions

What are Okazaki fragments?

• Short sequences of DNA nucleotides on the leading strand

• Short sequences of RNA nucleotides

• Short sequences of DNA nucleotides on the lagging strand

• Short sequences of DNA nucleotides on both strands

Which enzyme removes the RNA primer and replaces it with DNA?

• DNA ligase

• DNA polymerase III

• DNA polymerase I

• Helicase