BIO 250 MICROBIOLOGY FINAL EXAM 2026
FULL 60 QUESTIONS AND 100% CORRECT
ANSWERS GRADED A+
◉ Describe the transformation experiment you did in lab. Answer:
Transformation occurs when bacteria take up free-floating DNA
molecules that are present in the environment. In this lab, we had to
transform bacterial cells (E. coli) with plasmid DNA and observe the
new phenotypic traits that were acquired from genes that are expressed
from the plasmid.
◉ Describe the characteristics of a plasmid. Draw the pGLO plasmid.
Answer: The plasmid pGLO used in this lab contains and ori, an
ampicillin resistance gene (bla), and a gene encoding the green
fluorescent protein (GFP) that is under transcriptional control of the
arabinose promoter. The plasmid also encodes the arabinose repressor
(araC). The arabinose repressor binds to directly to the arabinose
promoter and prevents expression of GFP gene when there is no
arabinose present.
◉ List the components needed to set up a PCR reaction. Answer: Primer
mix, DNA template, and PCR bead.
◉ Describe the three steps in a PCR cycle. Illustrate what happens in
each step using DNA, primers, and Taq polymerase. Answer: 1st:
Denaturation occurs at 94°C when the hydrogen bonds in the DNA
double helix come apart resulting in single stranded DNA molecules.
, 2nd: Annealing at lower temperatures (45-65°C) when the primers base
pair with complementary sequences on the DNA molecules.
3rd: Extension occurs at 72°C when the thermostabile DNA polymerase
binds to the 3' ends of the primer and copies the DNA.
◉ Explain how PCR cycles create copies of target DNA. Answer: When
the temperature is decreased, short DNA sequences knows as primers,
bind or anneal to complementary matches on the target DNA sequence.
The primers bracket the target sequence to be copied.
◉ Explain the theory of agarose DNA gel electrophoresis. Answer:
Agarose gel electrophoresis is the easiest way to separate and analyze
DNA according to their size. Shorter molecules migrate more easily and
move faster than longer molecules through the pores of the gel and this
process is called sieving. The gel might be used to look at the DNA in
order to quantify it or isolate a particular band.
◉ Explain the purpose of SYBR green in agarose gel electrophoresis.
Answer: It is used as a dye for quantification of double stranded DNA in
some methods of PCR. It is also used to visualize DNA in gel
electrophoresis. Higher concentrations of this can be used to stain
agarose gels in order to visualize the DNA present.
◉ Explain why dilutions of a virus are incubated with bacteria followed
by plating in order to observe viral plaques. Answer: This is done to
create a plaque assay which is the quantitative amounts of viruses
produced in infected cells that can be measured with this. Doing the
FULL 60 QUESTIONS AND 100% CORRECT
ANSWERS GRADED A+
◉ Describe the transformation experiment you did in lab. Answer:
Transformation occurs when bacteria take up free-floating DNA
molecules that are present in the environment. In this lab, we had to
transform bacterial cells (E. coli) with plasmid DNA and observe the
new phenotypic traits that were acquired from genes that are expressed
from the plasmid.
◉ Describe the characteristics of a plasmid. Draw the pGLO plasmid.
Answer: The plasmid pGLO used in this lab contains and ori, an
ampicillin resistance gene (bla), and a gene encoding the green
fluorescent protein (GFP) that is under transcriptional control of the
arabinose promoter. The plasmid also encodes the arabinose repressor
(araC). The arabinose repressor binds to directly to the arabinose
promoter and prevents expression of GFP gene when there is no
arabinose present.
◉ List the components needed to set up a PCR reaction. Answer: Primer
mix, DNA template, and PCR bead.
◉ Describe the three steps in a PCR cycle. Illustrate what happens in
each step using DNA, primers, and Taq polymerase. Answer: 1st:
Denaturation occurs at 94°C when the hydrogen bonds in the DNA
double helix come apart resulting in single stranded DNA molecules.
, 2nd: Annealing at lower temperatures (45-65°C) when the primers base
pair with complementary sequences on the DNA molecules.
3rd: Extension occurs at 72°C when the thermostabile DNA polymerase
binds to the 3' ends of the primer and copies the DNA.
◉ Explain how PCR cycles create copies of target DNA. Answer: When
the temperature is decreased, short DNA sequences knows as primers,
bind or anneal to complementary matches on the target DNA sequence.
The primers bracket the target sequence to be copied.
◉ Explain the theory of agarose DNA gel electrophoresis. Answer:
Agarose gel electrophoresis is the easiest way to separate and analyze
DNA according to their size. Shorter molecules migrate more easily and
move faster than longer molecules through the pores of the gel and this
process is called sieving. The gel might be used to look at the DNA in
order to quantify it or isolate a particular band.
◉ Explain the purpose of SYBR green in agarose gel electrophoresis.
Answer: It is used as a dye for quantification of double stranded DNA in
some methods of PCR. It is also used to visualize DNA in gel
electrophoresis. Higher concentrations of this can be used to stain
agarose gels in order to visualize the DNA present.
◉ Explain why dilutions of a virus are incubated with bacteria followed
by plating in order to observe viral plaques. Answer: This is done to
create a plaque assay which is the quantitative amounts of viruses
produced in infected cells that can be measured with this. Doing the
