The health of dairy cows and humans
Tour of OSU Biochem labs (video)
Why are we so interested in the S. aureus bacterium?
a) It has the unique ability to increase milk production and thus lower milk prices
b) If found in an animal, S. aureus signifies the animal is healthy
c) It can infect both humans and animals
d) It can develop a resistance to antibiotics
e) Both a and b
f) Both c and d
What is MRSA?
a) Mathiosola-resistant S. aureus
b) Mitochondria-repeating S. aureus
c) Macomedia-repeating S. aureus
d) Macadonia-related S. aureus
e) Methicillin-resistant S. aureus
To determine if S. aureus was present in cow milk, the first step was to
a) Take milk samples and expose it to antibiotics
b) Take milk samples and grow bacterial cultures from it
c) Take milk samples and and pasteurize it
d) Take milk samples and compare it with milk sold in the grocery store
What is an “agar”?
a) A centrifuge used to separate bacteria from milk samples, allowing the researchers to
isolate S. aureus from all other bacteria as well as other milk molecules
b) A machine used to extract the DNA of bacteria
c) A biological agent used to kill S. aureus bacteria
d) A plate or “setting” which feeds some types of bacteria while inhibiting the
growth of other types of bacteria
[True or False?] Once your petri-dish looks like this, you are 100% certain that it is S. aureus
growing on the left side of the dish (your left).
To determine if a bacterium is S. aureus, researchers will inspect the DNA to see if it contains
a specific sequence of ____ letters.
a) 23
b) 230
c) 534
d) 5,340
e) 2,320
The goal of Polymerase Chain Reaction (PCR) is to
a) Locate and isolate a specific portion of DNA
b) Locate a specific portion of DNA and destroy the remaining DNA
c) Locate a specific portion of DNA and amplify the size of its nucleotides
d) Locate a specific portion of DNA and make millions of copies of it
The ingredients of PCR are primers, nucleotides, and polymerase. The ____ are like the
instructions for PCR.
a) Primers
b) Nucleotides
c) Polymerase
The ingredients of PCR are primers, nucleotides, and polymerase. The ____ are the
building-blocks of DNA.
a) Primers
b) Nucleotides
c) Polymerase
The ingredients of PCR are primers, nucleotides, and polymerase. The ____ does(do) the
work of PCR.
a) Primers
b) Nucleotides
c) Polymerase
In PCR, why is the DNA heated to 203 degrees Fahrenheit?
a) To separate the two sides of the DNA
b) To kill any remaining, live bacteria in the solution
c) To prevent the primers from building new DNA too fast
d) To preserve the DNA
What is the role of primers in PCR? (Note: a “strand” is one side of DNA.)
a) To tell the polymerase where on a DNA strand to start rebuilding DNA
b) To prevent either side of a DNA strand from separating
c) To determine the speed at which DNA is replicated
d) To determine the number of times in which DNA is replicated
e) Both c and d
After the first cycle in PCR, there are ___ complete strands, ___ lop-sided strands, and ___
short, targeted strands of DNA.
a) 1; 1; 0
b) 2; 2; 0
c) 1; 2; 1
d) 2; 4; 2
e) None of the above
After the second cycle in PCR, there are ___ complete strands, ___ lop-sided strands, and
___ short, targeted strands of DNA.
a) 2; 2; 1
b) 2; 2; 2
c) 2; 2; 4
d) 2; 4; 2
e) None of the above
Each additional cycle of PCR increases the number of whole DNA strands by ____, the
number of lop-sided strands by ____, and the number of short, targeted strands by ____.
a) 2; 4; more than 100%
b) 0; 4; more than 200%
c) 0; 2; more than 200%
d) 0; 2; more than 100%
e) 0; 2; more than 200%
[True or False] After many cycles of PCR, although the solution will contain two whole
DNA strands and some lop-sided DNA strands, if you pull out any DNA strand you are
virtually guaranteed it will be one of the short, targeted strands.
After PCR, gel electrophoresis is used to measure the ____ of the targeted DNA strands.
a) Width
b) Length
c) Electrical charge
d) Gravity
e) Sensitivity
Gel electrophoresis works by pushing the targeted DNA strands through a gel using ____.
a) An electric current
b) The weak force
c) Genetically modified bacteria or fungi
d) Gravity
e) Photons
In the output of gel electrophoresis below, the bars on the far left and far right are
a) The DNA segments themselves
b) Like yardsticks, helping to count the number of DNA segments of an equal size
c) Like yardsticks, used to measure the amount of certainty / uncertainty in PCR
d) Like yardsticks, helping to determine the length of a DNA segment
In the output of gel electrophoresis below, the which DNA segment is shorter?
a) A
b) B
c) Neither A nor B is a DNA segment
d) A and B are of the same length
[True or False?] Using PCR and gel electrophoresis, researchers proved that the S. aureus
that infected humans was not found in milk samples.
The picture below shows how the S. aureus was tested to determine if it had developed a
resistance to certain antibiotics. The small, vibrant white circles of a similar size are
a) Antibiotics
b) Areas where antibiotics killed S. aureus
c) Areas where S. aureus grew
The picture below shows how the S. aureus was tested to determine if it had developed a
resistance to certain antibiotics. The dark circles of varying size
a) Antibiotics
b) Areas where antibiotics killed S. aureus
c) Areas where S. aureus grew
The picture below shows how the S. aureus was tested to determine if it had developed a
resistance to certain antibiotics. The white streaks are
a) Antibiotics
b) Areas where antibiotics killed S. aureus
c) Areas where S. aureus grew
[True or False?] In the picture below, area A denotes an antibiotic in which the S. aureus has
developed a resistance to it.
[True or False?] In the picture below, area B denotes an antibiotic in which the S. aureus has
developed a resistance to it.
[True or False] The field of biotechnology changes fast, so fast that by the time this virtual
tour of the biochemistry lab is shown, understanding PCR will have very little educational
value.