📐 SAT
📝 ACT
🎓 AP Exams
About Contact Blog Privacy Policy

AP Biology — Unit 6 — DNA Replication — Drill 23

Drill 23 ·

0 / 5
0/5 correct

Nice work!

Review your answers above to learn from any mistakes.

← More Drills
←
Previous drill
Drill 22
Next drill
Drill 24
→
More AP Bio drills
Drill 1 5 questions → Drill 2 5 questions → Drill 3 5 questions → Drill 4 5 questions → Drill 5 5 questions → Drill 6 5 questions → Drill 7 5 questions → Drill 8 5 questions → Drill 9 5 questions → Drill 10 5 questions → Drill 11 5 questions → Drill 12 5 questions → Drill 13 5 questions → Drill 14 5 questions → Drill 15 5 questions → Drill 16 5 questions → Drill 17 5 questions → Drill 18 5 questions → Drill 19 5 questions → Drill 20 5 questions → Drill 21 5 questions → Drill 22 5 questions →
Drill 23 — current you are here
Drill 24 5 questions → Drill 25 5 questions → Drill 26 5 questions → Drill 27 5 questions → Drill 28 5 questions → Drill 29 5 questions → Drill 30 5 questions → Drill 31 5 questions → Drill 32 5 questions → Drill 33 5 questions → Drill 34 5 questions → Drill 35 5 questions → Drill 36 5 questions → Drill 37 5 questions →

About This Drill

AP Biology — Unit 6 — DNA Replication — Drill 23 is a practice drill. It contains 5 original questions created by Brian Stewart, a Barron's test prep author with over 20 years of tutoring experience.

Examine the mechanism of semi-conservative DNA replication and the key enzymes involved. Interpret the Meselson-Stahl experiment result to evaluate models of replication, and apply replication rules to predict outcomes of molecular scenarios.

Passage

DNA replication is a highly conserved, semi-conservative process. During replication, the double helix is unwound and each strand serves as a template for synthesis of a new complementary strand. Key enzymes include: helicase (unwinds the double helix at the replication fork), DNA polymerase III (synthesizes new DNA in the 5'->3' direction only), primase (synthesizes short RNA primers to initiate synthesis), DNA polymerase I (removes RNA primers and replaces them with DNA), and DNA ligase (seals nicks between Okazaki fragments on the lagging strand). A researcher conducts the Meselson-Stahl experiment: bacteria are grown for many generations in 15N (heavy nitrogen) medium so all DNA contains 15N. The bacteria are then transferred to 14N (light nitrogen) medium and allowed to replicate. DNA is extracted after each generation and centrifuged in a cesium chloride (CsCl) density gradient. Generation 1 result: All DNA molecules form a single band at an intermediate density (between pure 15N-15N and pure 14N-14N positions). Generation 2 result: Two bands appear -- one at intermediate density and one at light (14N-14N) density, in approximately equal proportions.

Questions in This Drill

  1. Which model of DNA replication is uniquely supported by both the Generation 1 and Generation 2 results of the Meselson-Stahl experiment taken together?
  2. On the lagging strand during DNA replication, synthesis is discontinuous, producing Okazaki fragments. Which sequence of molecular events correctly describes how a gap between two Okazaki fragments is resolved?
  3. A mutation eliminates the proofreading (3'->5' exonuclease) activity of DNA polymerase III. What would be the most likely consequence for DNA replication fidelity?
  4. DNA replication must occur before mitosis and meiosis. Which of the following accurately describes a key difference between how replication errors affect outcomes in mitosis versus meiosis?
  5. In eukaryotic DNA replication, multiple origins of replication fire simultaneously along each chromosome. Why is this feature essential for timely replication of eukaryotic genomes?