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Agro/ANSC/Gene/Hort/Bio 305
Fall, 2016
HW#7 (Due back on Nov 11)
Name:
Section:
1. In which of the ribosomal sites, the A site, P site, and/or E site, could the following be
found?
A. A tRNA without an amino acid:
B. A tRNA with a polypeptide attached:
C. A tRNA with a single amino acid attached:
D. A tRNA with fMet.
Q2. The following DNA sequence occurs in the nontemplate strand of a structural gene in
bacterium (the promoter sequence is located to the left but is not shown):
5’-GAATGTCAGAACTGCCATGCTTCATATGAATAGACCTCTAG-3’
a) What is the ribonucleotide sequence of mRNA molecule that is transcribed from
this piece of DNA?
b) What is the amino acid sequence encoded by this mRNA? Indicate both the amino
terminal and carboxy terminal ends.
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3. Transcriptional regulation often involves regulatory proteins that bind to a segment of
DNA and small effector molecule that binds to a regulatory protein. Do the following
terms apply to a regulatory protein, a segment of DNA or a small effector molecule?
a. Repressor
b. Inducer
c. operator
d. corepressor
e. activator
f. Attenuator
g. inhibitor
h. CAP site
i. lacZ
j. cAMP
k. Allolactose
l. Tryptophan
m. Enhancer
n. Mediator
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Q4. Drawn below is an outline of the lac operon. Label the lac operon and describe the
function of each element on the operon. The arrows point to the different elements/genes
in the operon.
_______________________________________________________________________
_______________________________________________________________________
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1.
2.
3.
4.
5.
6.
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Q5. How is the lac operon regulated when E. coli is grown both in the presence of
glucose and lactose?
Q6. What is the status of the trp operon in the following figure? Give an explanation for
your answer?
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Q7. Gene expression in eukaryotes is regulated at steps beyond transcription. Briefly,
describe these steps and give the mechanism of regulation.
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