CourseCourseConceptConceptDocsDocuments

IB Biology SL D1.1.2 Semi Conservative Replication Questions

Explore complementary template copying, one-old/one-new daughter molecules and Meselson–Stahl density patterns in IB Biology SL D1.1.2.

Syllabus
First assessment 2025
Course
Biology SL
Level
SL

Exam points

  • Distinguish semi-conservative replication by identifying one original strand paired with one newly synthesized strand in each daughter DNA molecule.
  • Explain how complementary base pairing on each pre-existing template gives accurate sequence copying.
  • Interpret Meselson–Stahl isotope-density patterns across replication rounds and contrast them with conservative replication.

IB Biology SL D1.1.2 Semi Conservative Replication Questions question 1

[Maximum number: 1]

Meselson and Stahl grew bacteria in a medium with 15 N{ }^{15} \mathrm{~N} (heavy nitrogen) so that all bacteria in the parental culture contain heavy DNA. They then transferred some of the bacteria to a medium with 14 N{ }^{14} \mathrm{~N} (light nitrogen).

Samples were taken at 0,20 and 40 minutes and centrifuged with the results as shown.

Figure for Question IB Biology SL D1.1.2 Semi Conservative Replication Questions question 1 — IB Biology SL

State the conclusion Meselson and Stahl drew from their experiment.

Up to one additional mark is available for the construction of your answer.

All question bank results loaded