Download Sample Final Exam Questions

Q1. A replication fork in a double-stranded (ds) DNA molecule found in a prokaryotic cell is shown
below. Each parent DNA strand is labeled A or B.
i) On which template strand (A or B) would there be continuous replication by DNA polymerase? What is
this newly synthesized daughter strand called during DNA replication?
ii) On which template strand (A or B) would there be discontinous replication by DNA polymerase? What
is this newly synthesized daughter strand called during DNA replication?
iii) Chemicals that inhibit the enzyme DNA polymerase I will primarily affect synthesis on one of the two
template strands (A or B). Explain on which template strand (A or B) polymerization will be primarily
affected and why this occurs.
Q2. The mars explorer found life on Mars! This new life form, named Mars bar, also uses DNA as its
genetic material. You are sent a sample of Mars bar to determine the mode of replication of its DNA.
You grow the organism in media which has 15N as the sole source of nitrogen for many generations
(analogous to the Meselson and Stahl experiment), and then transfer to media containing 14N as the
sole nitrogen source. When you analyze DNA from generation 0, 1 and 2, you are surprised to find that
this martian life form uses a conservative mode of replication to replicate its DNA. What were the
banding patterns you observed after ultracentrifugation for generations 0, 1 and 2 to make this
conclusion? Explain.
Q3. Which of the following is correct concerning a tRNA?
a) it contains a codon sequence.
b) it is the largest RNA in the cell.
c) it contains a poly A tail at the 3' end.
d) amino acids are attached to its 3' end.
e) tRNA is synthesized in the cytosol
Q4. Following is the sequence of a mRNA. 5’-ACCGGGUUU-3’
What would be the corresponding sequence of the DNA template strand? Please write the sequence in
the 5’ to 3’ direction.
Q5. Shown below is the structure of a monomer used in nucleic acid synthesis.
i) Would this monomer be used to form part of an RNA strand or a DNA strand? Briefly explain your
answer.
ii) In nucleic acid synthesis, one of the phosphate groups of this monomer is covalently linked to a new
strand that is being elongated. In the figure above, draw a circle around the phosphate group that would
be linked.
iii) When this monomer is already part of the newly synthesized strand, one of the hydroxyl groups of
this monomer will be linked to the phosphate group of the next monomer added. In the figure above,
draw a box around the hydroxyl group that will be linked.
Q6. The following illustrations show three petri dishes used for the Ames test. A piece of filter paper
soaked in water, Drug A and Drug B were placed in the middle of each dish, and a test strain of
salmonella plated on each dish. The results obtained after culturing the salmonella overnight are shown
below. The small circles indicate bacterial colonies. What can you conclude from these results?