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During translation, new tRNAs carrying amino
acids enter
of the ribosome.
A. The A site
B. The P site
C. The E site
D. The X site
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Which of the following is NOT true about
translation?
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A. Peptide bonds form between
the amino acids held by the
tRNAs in the P and A positions
B. tRNAs leave the ribosome
from the E position
C. tRNAs carrying their amino
acids enter the ribosome
initially at the P site
D. Amino acids are initially bound
to tRNAs at their carboxyl ends
2
Cycle repeats…
tRNA in E site
exits, and cycle
repeats (new
tRNA binds to A
site, etc.)
Translation movie
Termination:
Stop codons do not
specify any amino
acid
Release factor protein
binds to A site when
stop codon is reached
Termination:
Hydrolysis occurs to
break bond between
final amino acid and
its tRNA in the P
position
You are working at the Center for Disease Control (CDC), when
the rest of your team gets sick with an influenza virus they have
been studying. Your boss, Dr. Phillips, has given you the
responsibility of figuring out which virus they have, because
you are the only person on the team who is not sick.
In your conversation with Dr. Phillips, she says, “Here is the
situation. The team appears to have contracted an atypical flu
virus. The symptoms are worse than usual and none of the
team’s vaccinations protected them from this virus. We’re
worried that we are dealing with a new strain of influenza we
haven’t seen before. We need to figure out how this virus is
different.”
“I want you to compare the HA gene for the viruses the team
was examining with a typical flu virus. I will get you the
nucleotide sequence for a typical HA gene. You can start by
finding the coding region for the gene.”
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Flu virus contains hemagglutinin (H) and
neuraminidase (N)
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Hemagglutinin (HA)
• A glycoprotein
• An antigen that binds
with host cell receptors
to infect them
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Antibodies bind to antigens on viral membranes
to prevent their activity
• Binding is highly specific
• Changes in antigen = antibodies
no longer bind = no host cell
protection
Host cell receptor
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Influenza A virus: H and N can vary
among species
Flu vaccines typically contain H3N2, H1N1, and a B virus
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The types of antigens displayed on the
surface of a flu virus are a component of
the virus’
A. Genotype
B. Phenotype
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Vaccines train your body to produce antibodies that
“remember” the viral antigen…
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…as long as the antigen does not change!
Antigenic drift, caused by mutation, is common in influenza viruses
Changing the sequence of amino acids in
a protein could change its function by
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A. Altering the way the
protein folds
B. Altering the way the
protein interacts
with other molecules
C. Changing the 3-D
shape of the protein
D. All of the above
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3’-ATCGGCAGGACCTTAAAT-5’
5’-TAGCCGTCCTGGAATTTA-3’
**
If the DNA molecule above is a gene whose promoter lies to
the right of this sequence on the screen, which RNA can
be produced from this gene?
A.3′-ATCGGCAGGACCTTAAAT-5′
B. 5′-TAGCCGTCCTGGAATTTA-3′
C. 3′-AUCGGCAGGACCUUAAAU-5′
D. 5′-UAGCCGUCCUGGAAUUUA-3′
E. Both A and B
F. Both C and D
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5’CACGGUCGAUGAGGUUACAUAAC… 3’
**
Part of an mRNA molecule is shown above. If this fragment
came from the beginning of the mRNA, for which of the
amino acid sequences below would it most likely code?
A. His-Gly-Arg
B. Thr-Val-Asp-GluVal-Thr
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D. Gln-Tyr-Ile-GlyVal-Ala-Gly
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C. Met-Arg-Leu-HisAsn
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Dr. Phillips returned with a sheet of paper. “All I have
been able to find so far is a partial sequence I believe is at
the beginning of the HA gene.* I also found that the
promoter for this gene is to the right of the sequence given
here, and I have the start of the HA protein sequence. See
if you can find the coding region while I look for more
info.”
**
DNA Sequence
3’CTTACATCGAGTTTCGTTACTATCAGAAGTACCAAT 5’
5’GAATGTAGCTCAAAGCAATGATAGTCTTCATGGTTA 3’
HA amino acid sequence
Met Lys Thr Ile Ile Ala Leu Ser Tyr Ile…
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In this case, the bottom strand is transcribed
DNA
RNA
3’CTTACATCGAGTTTCGTTACTATCAGAAGTACCAAT 5’
5’GAATGTAGCTCAAAGCAATGATAGTCTTCATGGTTA 3’
3’CUUACAUCGAGUUUCGUUACUAUCAGAAGUACCAAU 5’
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DNA
3’CTTACATCGAGTTTCGTTACTATCAGAAGTACCAAT 5’
5’GAATGTAGCTCAAAGCAATGATAGTCTTCATGGTTA 3’
RNA
3’CUUACAUCGAGUUUCGUUACUAUCAGAAGUACCAAU 5’
RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3’
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RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3’
Reading frame-1
UAA CCA UGA AGA CUA UCA UUG CUU UGA GCU ACA UUC
Reading frame-2
U AAC CAU GAA GAC UAU CAU UGC UUU GAG CUA CAU UC
Reading frame-3
UA ACC AUG AAG ACU AUC AUU GCU UUG AGC UAC AUU C
RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3’
Reading frame-1
UAA CCA UGA AGA CUA UCA UUG CUU UGA GCU ACA UUC
Reading frame-2
U AAC CAU GAA GAC UAU CAU UGC UUU GAG CUA CAU UC
Reading frame-3
UA ACC AUG AAG ACU AUC AUU GCU UUG AGC UAC AUU C
Met Lys Thr Ile Ile Ala Leu Ser Tyr Ile
“Great! You found the start for the HA gene coding region.
Here are HA genes the team had collected for the flu
strains that they were studying. We only have information
on the start of the gene, but it might be enough.”
The virus that the team has contracted probably had a
mutation that results in a different, but still functional
version of the HA gene. See if one of the 4 strains of
viruses the team was examining would fit this description.
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**
Typical HA RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3’
Strain #1 RNA
5’UAACCAUGAGGACUAUCAUUGCUUUGAGCUACAUUC 3’
How is the HA protein produced by the new flu
virus different from a typical flu virus?
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A. There is no difference.
B. One amino acid has been
changed.
C. Several amino acids have been
changed.
D. The protein is too short.
E. The protein is too long.
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Typical HA RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3
Lys
Strain #1 RNA
5’UAACCAUGAGGACUAUCAUUGCUUUGAGCUACAUUC 3’
Arg
Mis-Sense (substitution)
Mutation
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**
Typical HA RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3
Strain #2 RNA
5’UAACCAUGAAGACUAUCAUUGCUUAGAGCUACAUUC 3’
How is the HA protein produced by the new flu
virus different from a typical flu virus?
ng
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A. There is no difference.
B. One amino acid has been
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C. Several amino acids have been
changed.
D. The protein is too short.
E. The protein is too long.
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Typical HA RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3
Leu
Strain #2 RNA
5’UAACCAUGAAGACUAUCAUUGCUUAGAGCUACAUUC 3’
Stop
Non-Sense Mutation
(truncation)
27
**
Typical HA RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3
Strain #3 RNA
5’UAACCAUGAAGACCAUCAUUGCUUUGAGCUACAUUC 3’
How is the HA protein produced by the new flu
virus different from a typical flu virus?
ng
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A. There is no difference.
B. One amino acid has been
changed.
C. Several amino acids have been
changed.
D. The protein is too short.
E. The protein is too long.
28
Typical HA RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3
Thr
Strain #3 RNA
5’UAACCAUGAAGACCAUCAUUGCUUUGAGCUACAUUC 3’
Thr
Silent Mutation
29
**
Typical HA RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3
Strain #4 RNA
5’UAACCAUGAAGACAUCAUUGCUUUGAGCUACAUUC 3’
How is the HA protein produced by the new flu
virus different from a typical flu virus?
ng
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A. There is no difference.
B. One amino acid has been
changed.
C. Several amino acids have been
changed.
D. The protein is too short.
E. The protein is too long.
30
Deletion of
this U
Typical HA RNA
5’UAACCAUGAAGACUAUCAUUGCUUUGAGCUACAUUC 3
Met Lys Thr Ile Ile Ala Leu Ser Tyr Ile
Strain #4 RNA
5’UAACCAUGAAGACAUCAUUGCUUUGAGCUACAUUC 3’
Met Lys Thr Ser Leu Leu STOP
Frame Shift Mutation:
alteration of reading frame
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Based on the information you have, which of
the four strains is most likely to be the one
causing the illness?
A. Strain 1 (mis-sense)
B. Strain 2 (non-sense)
C. Strain 3 (silent)
D. Strain 4 (frameshift)
)
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Be prepared to defend
your answer!!!
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On your note card:
• Name
• Date
• Explain, in terms of the central dogma, why
you need to get a new flu shot every year.
Explain your answer in terms of DNA,
RNA, protein, antigen, etc.
33