MICROBIOLOGY ALL LAB EXAM(2024-2025)
QUESTIONS WITH ANSWERS.
Why should you be careful not to overheat the smear during
the heat-fixing process? - <<<Answersa>>>overheating can
destroy to organism and the morphology of the cell can be
changed
Why do you think the presence of grease or dirt on a glass
slide will result in a poor smear preparation? -
<<<Answersa>>>may disrupt the amount of light coming
through,; can interfere with organism and change its
appearance
If the GAATTC palindrome is repeated four times on the
same piece of DNA, and the restriction enzyme that
recognizes that base sequence is present, how many DNA
fragments will be produced? - <<<Answersa>>>5
If the GAATTC palindrome repeats are randomly spaced
along the DNA strand, then what can you say about the size of
the fragments that will be produced? -
<<<Answersa>>>random sized fragments
Describe the evidence that indicates whether your attempt at
performing a genetic transformation was successful or not
successful. - <<<Answersa>>>A successful experiment will
be represented by the presence of colonies on the (+) pGLO
LB/amp and (+) pGLO LB/amp/ara plates and the absence of
, MICROBIOLOGY ALL LAB EXAM(2024-2025)
QUESTIONS WITH ANSWERS.
colonies on the (-) pGLO LB/amp plate. Moreover, the
colonies on the LB/amp/ara plate should fluoresce green. An
unsuccessful experiment will show an absence of colonies on
the (+) pGLO LB/amp and (+) pGLO LB/amp/ara plates. This
could be a result of not adding a loopful of plasmid to the (+)
pGLO tube or not adding a colony of bacteria to the (+) pGLO
tube.
Look again at your four plates. Do you observe some E. coli
growing on the LB plates which do not contain
ampicillin/arabinose? - <<<Answersa>>>Yes. The bacteria
that did not receive the plasmid are growing on a plain LB
plate.
From your results, can you tell if these bacteria are ampicillin
resistant by looking at them on the LB plate? Explain your
answer. - <<<Answersa>>>No. You cannot tell if the bacteria
are ampicillin resistant just by looking at them. Both types of
bacteria (those that are ampicillin resistant and those that are
ampicillin sensitive) look similar when cultured—think about
the colonies on the LB starter plate and the colonies on the
+pGLO LB/amp plate
How would you change the bacteria's environment to best tell
if they are ampicillin resistant? - <<<Answersa>>>The best
test would be to take some of the bacteria growing on the LB
plate and streak them on an LB/amp plate. If the bacteria are
viable on the LB/amp plate, then they are resistant to
, MICROBIOLOGY ALL LAB EXAM(2024-2025)
QUESTIONS WITH ANSWERS.
ampicillin. If no bacterial colonies survive, then they were not
ampicillin resistant (they were ampicillin sensitive).
What two factors must be present in the bacteria's
environment for you to see the green color? (Hint: one factor
is in the plate and the other factor is in how you
look at the bacteria). - <<<Answersa>>>The sugar arabinose
in the agarose plate is needed to turn on the expression of the
GFP gene. The UV light is necessary to cause the GFP protein
within the bacteria to fluoresce.
What do you think each of the two environmental factors you
listed above are doing to cause the genetically transformed
bacteria turn green? - <<<Answersa>>>The sugar arabinose
turns on expression of the GFP gene by binding to a
regulatory protein, araC, which sits on the PBAD promoter.
When arabinose is present, it binds to araC, consequently
changing the conformation of araC which facilitates
transcription of the gene by RNA polymerase (see detailed
description in Appendix D). Exposure to UV light causes GFP
to resonate, thereby giving off energy in the form of green
light.
What advantage would there be for an organism to be able to
turn on or off particular genes in response to certain
conditions? - <<<Answersa>>>Gene regulation allows for
adaptation to differing conditions and prevents wasteful
overproduction of unneeded proteins. Good examples of
QUESTIONS WITH ANSWERS.
Why should you be careful not to overheat the smear during
the heat-fixing process? - <<<Answersa>>>overheating can
destroy to organism and the morphology of the cell can be
changed
Why do you think the presence of grease or dirt on a glass
slide will result in a poor smear preparation? -
<<<Answersa>>>may disrupt the amount of light coming
through,; can interfere with organism and change its
appearance
If the GAATTC palindrome is repeated four times on the
same piece of DNA, and the restriction enzyme that
recognizes that base sequence is present, how many DNA
fragments will be produced? - <<<Answersa>>>5
If the GAATTC palindrome repeats are randomly spaced
along the DNA strand, then what can you say about the size of
the fragments that will be produced? -
<<<Answersa>>>random sized fragments
Describe the evidence that indicates whether your attempt at
performing a genetic transformation was successful or not
successful. - <<<Answersa>>>A successful experiment will
be represented by the presence of colonies on the (+) pGLO
LB/amp and (+) pGLO LB/amp/ara plates and the absence of
, MICROBIOLOGY ALL LAB EXAM(2024-2025)
QUESTIONS WITH ANSWERS.
colonies on the (-) pGLO LB/amp plate. Moreover, the
colonies on the LB/amp/ara plate should fluoresce green. An
unsuccessful experiment will show an absence of colonies on
the (+) pGLO LB/amp and (+) pGLO LB/amp/ara plates. This
could be a result of not adding a loopful of plasmid to the (+)
pGLO tube or not adding a colony of bacteria to the (+) pGLO
tube.
Look again at your four plates. Do you observe some E. coli
growing on the LB plates which do not contain
ampicillin/arabinose? - <<<Answersa>>>Yes. The bacteria
that did not receive the plasmid are growing on a plain LB
plate.
From your results, can you tell if these bacteria are ampicillin
resistant by looking at them on the LB plate? Explain your
answer. - <<<Answersa>>>No. You cannot tell if the bacteria
are ampicillin resistant just by looking at them. Both types of
bacteria (those that are ampicillin resistant and those that are
ampicillin sensitive) look similar when cultured—think about
the colonies on the LB starter plate and the colonies on the
+pGLO LB/amp plate
How would you change the bacteria's environment to best tell
if they are ampicillin resistant? - <<<Answersa>>>The best
test would be to take some of the bacteria growing on the LB
plate and streak them on an LB/amp plate. If the bacteria are
viable on the LB/amp plate, then they are resistant to
, MICROBIOLOGY ALL LAB EXAM(2024-2025)
QUESTIONS WITH ANSWERS.
ampicillin. If no bacterial colonies survive, then they were not
ampicillin resistant (they were ampicillin sensitive).
What two factors must be present in the bacteria's
environment for you to see the green color? (Hint: one factor
is in the plate and the other factor is in how you
look at the bacteria). - <<<Answersa>>>The sugar arabinose
in the agarose plate is needed to turn on the expression of the
GFP gene. The UV light is necessary to cause the GFP protein
within the bacteria to fluoresce.
What do you think each of the two environmental factors you
listed above are doing to cause the genetically transformed
bacteria turn green? - <<<Answersa>>>The sugar arabinose
turns on expression of the GFP gene by binding to a
regulatory protein, araC, which sits on the PBAD promoter.
When arabinose is present, it binds to araC, consequently
changing the conformation of araC which facilitates
transcription of the gene by RNA polymerase (see detailed
description in Appendix D). Exposure to UV light causes GFP
to resonate, thereby giving off energy in the form of green
light.
What advantage would there be for an organism to be able to
turn on or off particular genes in response to certain
conditions? - <<<Answersa>>>Gene regulation allows for
adaptation to differing conditions and prevents wasteful
overproduction of unneeded proteins. Good examples of
