Mastering DNA Replication Mechanisms and Key Enzymes

DNA replication starts at the origin of replication, where helicase unwinds the DNA helix. Single-strand binding proteins stabilize the unwound strands. DNA polymerase III adds nucleotides to the 3' end of a pre-existing chain, requiring an RNA primer made by primase. The leading strand is synthesized continuously, while the lagging strand forms Okazaki fragments. DNA polymerase I replaces RNA primers with DNA, and DNA ligase seals the fragments. DNA polymerase III functions as a dimer, replicating both strands simultaneously.

What is the role of helicase in DNA replication?

• It unwinds the double-stranded DNA helix.

• It synthesizes RNA primers.

• It adds nucleotides to the growing DNA strand.

• It stabilizes single-stranded DNA.

Why is an RNA primer necessary for DNA polymerase III?

• RNA primers are more stable than DNA primers.

• RNA primers prevent DNA tangling.

• DNA polymerase III can only add nucleotides to an existing chain.

• DNA polymerase III can initiate a nucleotide chain without a primer.

How does the leading strand differ from the lagging strand during DNA replication?

• The lagging strand does not require RNA primers.

• The leading strand is synthesized continuously.

• The leading strand is synthesized in short segments.

• The lagging strand is synthesized continuously.

What are Okazaki fragments?

• Short segments of DNA synthesized on the leading strand.

• Short segments of DNA synthesized on both strands.

• Short segments of RNA primers.

• Short segments of DNA synthesized on the lagging strand.

What is the function of DNA polymerase I during DNA replication?

• It synthesizes new DNA strands.

• It stabilizes single-stranded DNA.

• It replaces RNA primers with DNA.

• It unwinds the DNA helix.

How does DNA ligase contribute to DNA replication?

• It forms phosphodiester bonds between DNA fragments.

• It unwinds the DNA helix.

• It synthesizes RNA primers.

• It adds nucleotides to the growing DNA strand.

What is the current understanding of DNA polymerase III's function?

• It only replicates the lagging strand.

• It only replicates the leading strand.

• It functions as a dimer to replicate both strands simultaneously.

• It functions as separate units for each strand.

Why is the lagging strand folded during DNA replication?

• To allow simultaneous replication by the dimeric DNA polymerase.

• To stabilize the DNA helix.

• To increase the speed of replication.

• To prevent tangling of the DNA strands.