CLINICAL CASES
61
C O M P R E H E N SIO N Q U E ST IO N S
[6.1]
One of the steps in the PCR amplification of DNA fragments is the
denaturation step in which the temperature is raised to break the hydro-
gen bonds that make up the base pairing. Which of the following DNA
fragments would most likely require the greatest increase in tempera-
ture to cause complete denaturation?
A. 5'-C-A-A-T-G-T-A-A-T-T-G-C-A-T-3'
3'-G-T- T- A-C-A-T- T-A-A-C-G-T- A-5'
B. 5'-A-T-A-T-A-T-A-T-A-T-A-T-A-T -3'
3'-T- A-T- A-T- A-T- A-T- A-T- A-T- A-5'
C. 5'-A-A-C-C-G-G-A-C-C-G-C-G-A-T-3'
3'-T- T- G-G-C -C-T- G-G-C-G-C -T- A-5'
D. 5'-A-G-A-G-A-G-A-G-A-G-A-G-A-G-3'
3'-T-C-T-C-T-C-T-C-T-C-T-C-T-C-5'
E. 5'-G-A-C-T-G-T-A-A-T- A-C-G-A-T-3'
3'-C-T-G-A-C-A-T- T- A-T-G-C-T- A-5'
[6.2]
Restriction enzymes are used to cleave genomic DNA into smaller
fragments. Which of the following single-strand DNA sequences has
the best potential to be a site of action for a restriction endonuclease?
A. T-A-G-C-T-T
B. C-T-G-C-A-G
C. A-A-C-C-A-A
D. G-T-G-T-G-T
E. A-A-A-C-C-C
[6.3]
A 21-year-old woman was abducted when she went to the local con-
venience store. Her body was found the next morning in a wooded area
behind the store. The autopsy revealed that she had been sexually
assaulted and strangled. Crime scene investigators were able to collect
a semen sample from vaginal fluid as well as tissue samples from
underneath the victim’s fingernails. DNA samples were obtained from
three suspects besides the victim. A variable number of tandem repeats
(VNTR) analysis was performed on the DNA samples from the evidence
collected, the victim, and the suspect, and the results were compared.
Which of the following techniques is the most appropriately applied
for this analysis?
A. Allele-specific oligonucleotide probes
B. DNA sequencing
C. Northern blot
D. Southern blot
E. Western blot
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