The Meselson–Stahl experiment

Last updated: 17/02/2022

AQA A-Level Biology Nucleic acids are important information-carrying molecules The Meselson–Stahl experiment

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Question 1 of 20

1. Question
Who came up with the theory of semi-conservative DNA replication?
- Watson and Crick
- Watson and Stahl
- Meselson and Stahl
- Meselson and Crick
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Question 2 of 20

2. Question
Who validated the theory of semi-conservative DNA replication?
- Meselson and Stahl
- Watson and Stahl
- Watson and Crick
- Meselson and Crick
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Question 3 of 20

3. Question
What did Meselson and Stahl grow E. coli in?
- Two isotopes of nitrogen
- Two isotopes of hydrogen
- Two isotopes of carbon
- Two isotopes of oxygen
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Question 4 of 20

4. Question
Which of the following is an alternative to the semi-conservative model of DNA replication?
- The conservative model
- The liberal model
- The template replacement model
- The omni-conservative model
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Question 5 of 20

5. Question
Which of the following would best describe the conservative model of DNA replication?
- The original DNA molecule remains intact and a separate new molecule is made up of two new DNA strands
- The two new DNA molecules each contain one original and one new strand
- The original DNA molecule remains intact and a separate new molecule is made up of one original and one new DNA strand
- The new DNA molecule consists of four strands, two original and two new
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Question 6 of 20

6. Question
Which of the following was not one of the three facts that Meselson and Stahl based their experiment upon?
- Thymine is replaced by Uracil in RNA
- All bases in DNA contain nitrogen
- Nitrogen has two forms; the lighter 14N isotope and heavier 15N isotope
- Bacteria incorporate nitrogen from their medium into newly synthesized DNA
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Question 7 of 20

7. Question
How did Meselson and Stahl separate DNA strands containing different proportions of heavy and light nitrogen isotopes?
- Centifugation
- Filtration
- X-ray diffraction
- Microscopy
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Question 8 of 20

8. Question
Centrifugation separates components based on what?
- Density
- Size
- Charge
- The presence of nitrogen
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Question 9 of 20

9. Question
What does centrifugation involve?
- Spinning a vessel rapidly
- Applying electrical charge across a vessel
- Bombarding a sample with radiation
- Forcing the contents of a vessel though a fine filter
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Question 10 of 20

10. Question
Which force was used to separate the heavy and light DNA molecules in Meselson and Stahl’s experiment?
- Centrifugal force
- Frictional force
- Electromagnetic force
- Strong nuclear force
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Question 11 of 20

11. Question
Where would DNA containing only the lighter 14N isotope be expected to be in the centrifuge tube?
- Nearer to the top
- Nearer to the bottom
- In the middle
- At the bottom
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Question 12 of 20

12. Question
Where was DNA containing only the heavier 15N isotope be expected to be in the centrifuge tube?
- Nearer to the bottom
- Nearer to the top
- In the middle
- At the top
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Question 13 of 20

13. Question
In Meselson and Stahl’s experiment, which of the following statements would be correct if the conservative model of DNA replication held true?
- There would be a DNA molecule with both strands containing heavy 15N in every generation
- There would be a DNA molecule with both strands containing heavy 15N in only the first generation
- In the first generation there would be a mixed DNA molecule with heavy 15N and light 14N
- In the second generation there would be a mixed DNA molecule with heavy 15N and light 14N as well as a light DNA molecule with only 14N
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Question 14 of 20

14. Question
In Meselson and Stahl’s experiment, which of the following statements would be be correct if the semi-conservative model of DNA replication held true?
- In the second generation there would be a mixed DNA molecule with heavy 15N and light 14N as well as a light DNA molecule with only 14N
- There would be a DNA molecule with both strands containing heavy 15N in every generation
- There would be a DNA molecule with both strands containing heavy 15N in only the first generation
- There would never be a DNA molecule containing only light 14N in any generation
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Question 15 of 20

15. Question
After one generation, why was all of the DNA found to be an equal mixture of 14N and 15N?
- Because DNA replication is semi-conservative
- Because DNA replication is conservative
- Because DNA replication had not yet occurred
- Because the bacteria had undergone meiosis
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Question 16 of 20

16. Question
If Meselson and Stahl continued their experiment longer, after 10 generations growing in 14N medium, which of the following would be true?
- DNA molecules would mostly contain only light 14N, but a small number would contain both light 14N and heavy 15N
- DNA molecules would contain only heavy 15N
- DNA molecules would contain only light 14N
- DNA molecules would mostly contain only heavy 15N, but a small number would contain both light 14N and heavy 15N
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Question 17 of 20

17. Question
Which part of DNA contains nitrogen?
- Organic base
- Pentose sugar
- Phosphate group
- Phosphodiester bond
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Question 18 of 20

18. Question
Which of the following is not a good reason for Meselson and Stahl to have used E. coli for their experiment
- Semi-conservative DNA replication only occurs in bacteria
- E. coli grows and divides quickly
- E. coli can be labelled by including different isotopes in the growth media
- DNA can be easily extracted from E. coli
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Question 19 of 20

19. Question
The replication of DNA of which of the following occurs semi-conservatively? 1. Bacteria 2. Fungi 3. Humans 4. Viruses
- All of the above
- 1 only
- 1, 2 & 3
- 1 &3
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Question 20 of 20

20. Question
Which isotopes were used by Meselson and Stahl?
- 14N and 15N
- 13N and 14N
- 13N and 15N
- 14N and 23N
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