2.2 dna replication Flashcards
Q: What is the purpose of DNA replication?
A: To produce two identical copies of DNA, ensuring genetic continuity between generations of cells.
Q: What type of replication does DNA
A: Semi-conservative replication.
What does semi-conservative replication mean?
A: Each new DNA molecule consists of one original (parent) strand and one newly synthesized strand.
Q: Which enzyme unwinds the DNA double helix?
A: DNA helicase.
Q: How does DNA helicase unwind DNA?
A: By breaking the hydrogen bonds between complementary base pairs.
Q: What happens to the exposed strands after the DNA is unwound?
A: They act as templates for the synthesis of new complementary strands.
Q: Which enzyme synthesizes the new DNA strand?
A: DNA polymerase.
Q: How does DNA polymerase work?
A: It joins free nucleotides to the template strand via complementary base pairing, forming phosphodiester bonds.
Q: What is the role of free nucleotides in DNA replication?
A: They pair with the exposed bases on the template strand using complementary base pairing (A-T and G-C).
Q: What is the direction of synthesis for the new DNA strand?
A: DNA polymerase synthesizes in the 5’ to 3’ direction.
Q: Why is the replication process described as “antiparallel”?
A: Because the two strands of the DNA molecule run in opposite directions.
Q: What is the leading strand?
A: The strand synthesized continuously in the 5’ to 3’ direction.
Q: What is the lagging strand?
A: The strand synthesized discontinuously in short sections called Okazaki fragments.
Q: What enzyme joins Okazaki fragments on the lagging strand?
A: DNA ligase.
Q: What experiment demonstrated the semi-conservative model of DNA replication?
A: Meselson and Stahl’s experiment with heavy (15N) and light (14N) isotopes of nitrogen.
