Mississippi Science GEN.1B.1
The Standard
- GEN.1B
- Students will analyze how the DNA sequence is copied and transmitted to new cells.
Compare and contrast various proposed models of DNA replication (i.e., conservative, semi-conservative, and disruptive). Evaluate the evidence used to determine the mechanism of DNA replication.
2026 Mississippi College- and Career-Readiness Standards for Science · Structure and Function of DNA
Teacher's field guide
What This Standard Means
What Students Need to Do
- Students show where the original DNA ends up in each proposed copying model. They use results from bacteria grown first with heavy nitrogen, then with light nitrogen, to decide which model fits.
What Mastery Looks Like
- A student predicts the DNA bands each model would produce after one and two rounds of copying. They explain why an intermediate band after one round rules out the conservative model, and why separate intermediate and light bands after two rounds rule out the dispersive model.
Common Misconceptions
- Students may think an intermediate band after one round proves the semiconservative model, but the dispersive model predicts one too. They may also confuse one old strand paired with one new strand with old and new pieces mixed along each strand.
How to Assess It
- Give this exit ticket: Bacteria grown in heavy nitrogen are moved to light nitrogen. Their DNA shows one intermediate band after one round, then intermediate and light bands after two rounds. Which model fits, and what rules out each other model?
Lesson moves
Ways to Teach It
Give pairs red old-strand and blue new-strand paper strips; have them cut and arrange daughter DNA after two rounds for each model.
Ask students to write why one intermediate band after the first round does not settle the question.
Hand out cards showing DNA band patterns; students match each card to a model and a round of copying.
Show a photo of a centrifuge tube from the bacterial experiment; ask students what the band positions reveal about DNA copying.
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Related Standards
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Students will analyze how the DNA sequence is copied and transmitted to new cells.
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