Table of contents

1. Introduction to Genetics51m
2. Mendel's Laws of Inheritance3h 37m
3. Extensions to Mendelian Inheritance2h 41m
4. Genetic Mapping and Linkage2h 28m
5. Genetics of Bacteria and Viruses1h 21m
6. Chromosomal Variation1h 48m
7. DNA and Chromosome Structure56m
8. DNA Replication1h 10m
9. Mitosis and Meiosis1h 34m
10. Transcription1h 0m
11. Translation58m
12. Gene Regulation in Prokaryotes1h 19m
13. Gene Regulation in Eukaryotes44m
14. Genetic Control of Development44m
15. Genomes and Genomics1h 50m
16. Transposable Elements47m
17. Mutation, Repair, and Recombination1h 6m
18. Molecular Genetic Tools19m
- Genetic Cloning
  9m
- Methods for Analyzing DNA
  9m
19. Cancer Genetics29m
- Overview of Cancer
  21m
- Cancer Mutations
  7m
20. Quantitative Genetics1h 26m
21. Population Genetics50m
- Hardy Weinberg
  19m
- Allelic Frequency Changes
  31m
22. Evolutionary Genetics29m

7. DNA and Chromosome Structure

DNA as the Genetic Material

Genetics

7. DNA and Chromosome Structure

DNA as the Genetic Material

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Multiple Choice

The banding patterns of the DNA fragments in the Meselson-Stahl experiment reveal that:

DNA replication is dispersive, with each strand being a mix of old and new DNA segments.

DNA replication is conservative, with one molecule containing both old strands and the other both new strands.

DNA replication is semiconservative, with each daughter molecule containing one old and one new strand.

DNA fragments are identical in density regardless of replication method.

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Verified step by step guidance

Understand the Meselson-Stahl experiment setup: They grew bacteria in a heavy isotope of nitrogen (\(^{15}N\)) and then shifted them to a lighter isotope (\(^{14}N\)) to track DNA replication over generations.

Recognize that DNA replication models predict different distributions of DNA densities after replication: conservative replication predicts separate heavy and light DNA molecules; semiconservative predicts hybrid molecules with one old and one new strand; dispersive predicts mixed strands throughout each molecule.

Analyze the banding patterns observed after centrifugation: after one round of replication, a single intermediate density band appears, which rules out conservative replication because no separate heavy band remains.

After subsequent rounds, observe the appearance of both light and intermediate bands, which is inconsistent with dispersive replication that would produce only intermediate density bands.

Conclude that the pattern of one intermediate band after the first replication and both intermediate and light bands after further replications supports the semiconservative model, where each daughter DNA molecule contains one old and one new strand.