Download Chapter 3,

Bauman Chapter 8 Answers to Critical Thinking Questions
Chapter 8
p. 244
Even though some students correctly synthesize a fluorescent cDNA probe
complementary to mRNA for a particular yeast protein, they find that the probe does not
attach to any portion of the yeast’s genome. Explain why the students’ probe does not
work.
The cDNA probe sequence spans a splice junction in the mRNA, therefore there is no
sequence in the genome that corresponds to the probe sequence. The short sequences
in the genomic DNA flanking the splice junction are insufficient to form a stable duplex
with the cDNA probe.
p. 252
If the restriction enzymes HindIll and BamHl together produce restriction fragments 1.08
kbp and 1.32 kbp, then which of the three maps shown in Figure 8.10 is correct?
The map on the left in Figure 8.10 is the correct map of the plasmid. The total plasmid
length is 2.4 kbp. In the left hand map the distances between the HindIII and BamHI
sites are 45% (1.08 kbp) and 55% (1.32 kbp) apart.
p. 261
1.
Examine the restriction sites listed in Table 8.1. Which restriction enzymes produce
restriction fragments with sticky ends? Which produce fragments with blunt ends?
Restriction enzymes BamHI, EcoRI, HindIII, and HinfI produce sticky ends. Restriction
enzymes EcoRII, HindII, HpaI, MspI, and SmaI produce blunt ends.
2.
A cancer-inducing virus, HTLV-1, inserts itself into a human chromosome, where it
remains. How can a laboratory technician prove that a patient is infected with HTLV-1?
The technician can design a DNA probe—a radioactive or fluorescent DNA strand that is
complimentary to a specific sequence found in HTLV-1 but not in the human genome.
Hybridization of the probe with DNA from a patient, as visualized by finding radioactivity
or fluorescence in the hybrid DNA, demonstrates the presence of HTLV-1 DNA in the
sample.
3.
A thermocycler uses DNA polymerase from hyperthermophilic prokaryotes, but it
cannot use DNA polymerase derived from Escherichia coli. Why not?
The temperature used in a thermocycler for DNA amplification far exceeds the
temperature maximum of mesophilic Escherichia coli, therefore DNA polymerase of E.
coli would denature and lose function in a thermocycler.