Biol 131
Questions Bank
DNA
1. DNA replication is said to be semiconservative because
A. synthesis can proceed uninterrupted (as a leading strand) in only one direction.
B. each new DNA molecule contains one preexisting strand and one new strand.
C. after each round of DNA replication, the original DNA double helix is still intact.
D. the original base sequence is conserved in the daughter DNA molecules.
2. Name the scientists who:
A. showed that different species possess DNA with different ratios of nitrogenous bases:
_____________________________.
B. showed that bacteria can acquire new genetic information from their surroundings:
_______________________; and who later showed that that genetic information appeared
to be nucleic acids: _____________________.
C. generated the first high quality X-ray diffraction images of DNA:
________________________.
D. showed that viruses pass DNA not protein to cells that they infect:
________________________.
E. elucidated the three dimensional structure of the DNA molecule:
________________________.
F. showed that DNA replication is semiconservative: ____________________________.
3. In the experiments carried out by Hershey-Chase, bacteriophage viruses were labeled with either
radioactive phosphorous (32P) or sulfur (35S).
A. Which one of these radionucleotides labels protein? Why? _______________________
________________________________________________________________________
B. Which one of these radionucleotides labels nucleic acids? Why? ___________________
________________________________________________________________________
C. What result would have been obtained if instead the bacteriophages were labeled with
radioactive nitrogen (13N)? Explain. _________________________________________
________________________________________________________________________
________________________________________________________________________
4. Complete the following table
Species
A
B
C
D
Adenine
23
18
20
Percentage of each base
Cytosine
Thymine
27
23
32
20
Guanine
24
Who discovered the relationships shown in the above table? _________________________
Biol 131
Question Bank
DNA
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5. Frederick Griffith carried out a series of experiments using pathogenic (encapsulated) and nonpathogenic (non-encapsulated) strains of the bacterium Streptococcus pneumoniae. The most
important finding of his experiments was that:
A. Information about the traits of a cell could be passed between organisms.
B. DNA appeared to carry the genetic information of the cell.
C. The capsule of this species of bacteria is necessary for it to cause disease.
D. Mutation in DNA can alter the traits of a cell.
6. The experiments of T. Oswald Avery extended the findings of Griffith by demonstrating that
____ (select answer from above).
7. Suppose you replicated the experiment of Meselson and Stahl, growing the cells on media
containing 15N, and then transferring them to media containing 14N. Which generation of cell
division after being transferred to the 14N media would yield DNA that contained 75% light
density DNA and 25% intermediate density DNA?
A. F1
D. F4
B. F2
E. F5
C. F3
Explain your answer.
8. The diagram to the right shows a new nucleotide
triphosphate about to be added to the end of a
DNA strand.
A. To the right redraw the diagram with the
new nucleotide connected with a
phosphodiester linkage.
B. Circle the phosphodiester linkage in your
drawing.
C. What are the two products of this
dehydration synthesis reaction?
_________________________________
9. In the diagram below, number the carbons
of the deoxyribose in their proper sequence.
Biol 131
Question Bank
DNA
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10. In the diagram to the right:
A. label the 3’ and 5’ ends of the strand.
B. label each base as being either a purine
or a pyrimindine.
11. As a new DNA strand is being synthesized, it elongates in
both directions. Which one of these processes:
1) elongation of the leading strand, or
2) creation of new lagging strands
contributes to elongation of the new strand on the:
A. 3’ end? ____
B. 5’ end? ____
12. A. Which one of the following answers correctly shows the orientation of strands in the DNA
double helix?
1. 3’ - ATGCATGCATGCATGC – 5’
3’ - ATGCTAGCATGCATGC – 5’
4. 3’ - ATGCATGCATGCATGC – 5’
5’ - TACGTACGTACGTACG – 3’
2. 3’ - ATGCATGCATGCATGC – 5’
5’ - ATGCTAGCATGCATGC – 3’
5. 3’ - ATGCATGCATGCATGC – 5’
5’ - CGTACGTACGTACGTA – 3’
3. 3’ - ATGCATGCATGCATGC – 5’
3’ - TACGTACGTACGTACG – 5’
B. In #3 above, circle an example of an ‘AT’ base-pair and an example of a ‘GC’ base-pair.
C. Write in the base sequence that is complementary to this:
3’ – A A G C T C G A T T C G – 5’
Now explain why each of these statements is false:
1. “The DNA sequence in the two strands of the double helix are identical but run in the
opposite directions.”
2. “The DNA sequence in the two strands of the double helix are independent of each other.”
13. Replication of DNA requires a primer to initiate DNA synthesis because DNA polymerase can
add new nucleotides:
A. only to an RNA chain.
C. only in the 5-to-3 direction.
B. only to a base-paired nucleotide.
D. only in short fragments.
Biol 131
Question Bank
DNA
Page 3
14. The line below represents a single DNA strand and the position of a replication origin.
A. Below the strand, show the arrangement of the complementary leading strand and two
lagging strands (as simple lines and arrows) as they would be arranged around the
replication origin.
B. Label the 5’ and 3’ ends.
C. For the new strands, indicate the expected positions of the RNA primer, DNA strand and
DNA polymerase III.
Repl origin
3’_________________________________________________________5’ template
||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||||
15 In the diagram below the light lines indicate the template strands and the dark lines indicate new
complementary strands.
Indicate where the replication origin was located with an ‘X’.
Label the 5’ and 3’ends of the new strands.
Label the leading-strand and lagging-strands.
Add arrowheads to the dark lines to show the direction in which the newly made DNA
strands were synthesized.
E. Number the Okazaki fragments on each strand 1, 2, and 3 in the order in which they were
synthesized (1 first, 3 most recently).
F. Indicate the direction of movement of the replication forks with arrows.
A.
B.
C.
D.
16. During the synthesis of each new Okazaki fragment, the following enzymes operate sequentially.
A. Next to each protein, add a number to indicate the order in which the proteins function
during the synthesis of a new stretch of DNA.
____ DNA ligase - _____________________________________________________
____ DNA exonuclease/polymerase – I - ___________________________________
____ DNA helicase - ___________________________________________________
____ DNA polymerase – III - ____________________________________________
____ RNA primase - ___________________________________________________
B. Briefly describe the function of each protein.
Biol 131
Question Bank
DNA
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17. A mutation would be best described as
A. any change to a cell that affects its function.
B. a change in the shape of a protein.
C. a change in the base sequence of DNA.
18. A thymine dimer would be best described as
A. a base substitution
B. a base deletion
C. chromosome aberration
D. a chemical modification
19. Excision repair of DNA requires both the action of a DNA endonuclease, ligase, and DNA
polymerase. Describe the function of each enzyme during this process.
DNA endonuclease:
DNA ligase:
DNA polymerase:
20. Proof-reading during DNA replication refers to:
A. removal of the RNA primer before connecting Okazaki fragments.
B. pairing of A with T and G with C by DNA polymerase.
C. removal of thymine dimers by excision repair.
D. checking for correct base pairing by DNA polymerase.
21. The relationship between the sequences of bases in DNA and amino acids in protein would be
best stated as:
A. The sequence of nucleotides in DNA is determined by the amino acid sequence of DNA
polymerase.
B. The sequence of nucleotides in a DNA is determined by the amino acids in proteins.
C. The sequence of amino acids is determined by the relative percentages of A, T, G and C in
the DNA.
D. The sequence of amino acids is determined by the sequence of nucleotides in a gene.
Biol 131
Question Bank
DNA
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22. Watson and Crick, although they did not perform any specific laboratory-based experiments
themselves were awarded the Nobel Prize for elucidating the structure of the DNA double helix.
A. Whose X-ray diffraction data helped them to solve the structure? ___________________
B. What are three important features of the structure of DNA that they figured out?
1.
2.
3.
Biol 131
Question Bank
DNA
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