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Bio 219 Final Exam: Questions With Solutions (100%)
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Bio 219 Final Exam: Questions With Solutions (100%)
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Bio 219 Final Exam: Questions With Solutions (100%)There are two purposes to our quarter-long project. What are they? Right
Ans - a. The first aspect is to isolate the lux operon from Aliivibrio fischeri
genomic DNA and transform E. coli to induce bioluminescence
b. The second goal is to quantify gene expression changes in E. coli after
transformation using the GadA system
What bioluminescent bacterial organism did we use? Right Ans - Alivibirio
fischeri
Explain the symbiotic relationship between this organism and the creatures
that house it. Right Ans - Benefit to host (fish or squid)
a. Communication
b. Attracting prey
c. Hiding from predators
d. Attracting a mate
Benefit to bacteria
e. Reliable food source
f. Glucose
g. Amino Acids
h. Protection
Give two examples of marine organisms that take part in this symbiotic
relationship. Right Ans - i. MJ 1741 Monocentris japonica (pineapple fish).
ii. ES 114 (700601) from Eupryma scolpes (Bobtail squid)
Describe the lux operon. What is it, what is its size, what components does it
contain, and what are these individual components responsible for? Right
Ans - About 9kb. Oxidation of luciferin catalyzed by luciferase. Lux operon
responsible for the transcription of chemical components involved in light
production. LuxI encodes for the autoinducer synthase. LuxR encodes for the
transcriptional activator that binds the auto inducer.
What biochemical reaction causes bioluminescence? Be able to describe and
write out the reaction. Right Ans - FMNH2 + O2 + RCHO → FMN + RCOOH +
H2O + light
, Molecular oxygen oxidizes flavin mononucleotide and a long chain aliphatic
aldehyde to an aliphatic carboxylic acid. Forms an excited hydroxyfavin
intermediate which is dehydrates to product of FMN to emit light
What is quorum sensing? Right Ans - Regulation of gene expression in
response to changes in cell-population density
Describe auto-induction Right Ans - Bacteria release a small metabolic
product (N-acyl homoserine-lactone). AHL diffuses freely across cell
membrane into an extracellular environment. Density goes up, more inducer
is increased. When a critical concentration of the inducer is present, the
inducer diffuses back into the cells and interacts with specific factors which
results in gene expression.
What is the E.Coli LuxR homolog? Can E-Coli use quorum sensing? If so how
does E-Coli do this in nature? Right Ans - E.coli encodes the LuxR homolog,
SdiA to detect AHL. It lacks the gene to make the autoinducer but can response
to AHL. The SdiA detects AHL and induces up-regulation of gadAx operon
which contains the GadA gene.
a. What is the GADAX operon? What does it encode? What gene are we
focusing on? What should happen to that gene's expression in the presence of
the Lux operon? What reference gene will we be using as a comparison to the
gene in question? Right Ans - GadA encodes for a glutamate decarboxylase
that plays a role in acid tolerance. If lux is present, then the gadA gene is
significantly upregulated due to AHL being present.
Describe the structure of bacterial chromosomes. Right Ans - Located in
the nucleoid. They are "naked" DNA. The bacteria have one contiguous (closed
loop) of double stranded DNA- making it circular.
Resuspension buffer Right Ans - This contains Sodium dodecyl sulphate
(SDS) which is a strong anionic detergent that can solubilize membrane
proteins. It disrupts the lipid bilayer and brings proteins into solution as
protein-lipid-detergent complexes. The phospholipids in the membrane are
solubilized by detergent. The SDS releases the DNA binding proteins by
denaturing them and binding both membrane and non- membrane proteins as
monomers.
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