MICROBIOLOGY REVIEWED QUESTIONS AND THEIR EXPECTED CORRECT ANSWERS

MICROBIOLOGY REVIEWED
QUESTIONS AND THEIR
EXPECTED CORRECT ANSWERS
Why is PCR a valuable technique?

PCR stimulates transcription of genes (DNA).
PCR creates large amounts of DNA from minute source
quantities.
PCR separates DNA from crude mixtures of other
biomolecules.
PCR harvests small quantities of DNA.
PCR creates large amounts of DNA from minute source
quantities.
Which of the following best describes the purpose of primers
in PCR?

To provide a template for free nucleotides
To separate double-stranded DNA into single strands
To provide a structure from which DNA can be synthesized
To activate DNA polymerase to replicate DNA
To provide a structure from which DNA can be synthesized
What does a thermocycler do?

,Monitors the synthesis of DNA
Adds reagents to facilitate the PCR run
Subjects samples to temperature changes
Purifies DNA from a crude sample
Subjects samples to temperature changes
In PCR, it is important to use Taq DNA polymerase, as opposed
to other DNA polymerases. This is because Taq is capable of
synthesizing DNA _________.

at 55∘∘C
at 94∘∘C
from user-provided DNA and primers
after exposure to 94∘∘C
after exposure to 94.
Each step of the polymerase chain reaction is associated with
a particular temperature.
Match the temperatures in the left column with the
appropriate PCR stage on the right.
72C = DNA extension
55C= Primer annealing
94C= DNA denaturation
The following tiles indicate the first five thermocycler steps in
a PCR run. Arrange them in the correct order.

,94 for 1 minutes
55 for 1 minutes
72 for 1 minute
94 for 1 minutes
55 for 1 minute
After the 94C step, why must the thermocycler reduce the
temperature to 55C?

To allow the DNA template strands to bind to each other
To separate the DNA template strands
To allow primers to bind to the DNA template strands
To optimize DNA polymerase activity
To allow primers to bind to the DNA template strands
Which of the following best describes why PCR protocols
contain numerous cycles of the
denaturation/annealing/extension steps?

The denaturation step of each cycle only separates some of
the source DNA. By performing numerous cycles, PCR
generates copies of all the target sequences.

Each cycle of PCR allows Taq polymerase to partially
synthesize the target sequence. Numerous cycles are
necessary for the target sequence to be fully copied.

Each cycle of PCR incorporates some of the included primers

, into amplicons. Numerous cycles of PCR are required to
ensure all primers are incorporated.

Each cycle of PCR doubles the amount of DNA synthesized, but
the number of copies starts out small. Numerous cycles are
required to produce a sufficient number of copies.
Each cycle of PCR doubles the amount of DNA synthesized, but
the number of copies starts out small. Numerous cycles are
required to produce a sufficient number of copies.
Suppose the thermocycler is INCORRECTLY programmed to
omit the 72C step in each cycle of an otherwise normal PCR
run. Which of the following would most likely occur?

DNA polymerase would synthesize DNA more slowly.
DNA polymerase would be active at 94∘∘C.
Primers would NOT bind to DNA template strands.
DNA template strands would bind to each other.
DNA polymerase would synthesize DNA more slowly.
Which of the following statements about recombinant DNA
technology is FALSE?

It allows researchers to make protein products of a gene.
It allows researchers to make many copies of a gene of
interest.
It can be used to screen individuals for many different types of