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Molecular Biology > Lecture 8: DNA Translation > Flashcards

Lecture 8: DNA Translation Flashcards

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1
Q

What is the role of aminoacyl-tRNA synthetase in tRNA charging?
a) It adds the amino acid to the 3’ end of the tRNA.
b) It adds AMP directly to the tRNA.
c) It removes the pyrophosphate from ATP.

A

a)

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2
Q

What happens to ATP during the activation of an amino acid?
a) It is completely broken down into AMP and PPi.
b) It remains unchanged.
c) It becomes ADP.

A

a)

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3
Q

What is the intermediate molecule formed during tRNA charging?
a) Aminoacyl-AMP
b) Aminoacyl-tRNA
c) AMP and pyrophosphate

A

a)

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4
Q

Where is the amino acid attached on the tRNA?
a) The anticodon loop
b) The 5’ end of the tRNA
c) The 3’ end of the tRNA

A

c)

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5
Q

What happens to AMP during tRNA charging?
a) It remains attached to the tRNA.
b) It is released when the amino acid is transferred to the tRNA.
c) It provides energy for peptide bond formation.

A

b)

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6
Q

What provides the energy to form a peptide bond during translation?
a) ATP stored in the tRNA
b) The high-energy bond between the tRNA and the amino acid
c) AMP attached to the amino acid

A

a)

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7
Q

Which tRNA site in the ribosome holds the tRNA with the growing polypeptide chain?
a) A-site
b) P-site
c) E-site

A

b) P site

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8
Q

What happens to the spent tRNA after it transfers its amino acid?
a) It moves to the E-site and exits the ribosome.
b) It returns to the A-site for reuse.
c) It is immediately recharged with another amino acid.

A

a)

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9
Q

What binds at the A-site of the ribosome during translation?
a) The growing polypeptide chain
b) An activated aminoacyl-tRNA
c) An mRNA codon

A

b)

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10
Q

During translation elongation, how many nucleotides does the ribosome shift down the mRNA?
a) 1 nucleotide
b) 3 nucleotides
c) 6 nucleotides

A

b)

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11
Q

What does the AUG codon specify?
a) The start of translation and methionine
b) The end of translation
c) The attachment site for tRNA

A

a)

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12
Q

How does the ribosome select the correct AUG in eukaryotes?
a) By recognizing the Shine-Dalgarno sequence
b) By locating the first AUG near the 5’ cap of the mRNA
c) By identifying the stop codon

A

b)

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13
Q

Why is it important to select the correct AUG codon?
a) It determines the length and amino acid sequence of the protein.
b) It helps the ribosome bind to the mRNA.
c) It terminates translation.

A

a)

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14
Q

What happens if the ribosome chooses the wrong AUG?
a) The protein will be correct.
b) A different protein will be produced.
c) Translation will not occur.

A

b)

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15
Q

How many reading frames exist for any given mRNA sequence?
a) 1
b) 3
c) 6
d) none of the above

A

b)

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16
Q

How does the ribosome know which AUG is the starting codon since there are many AUGs in one reading frame? (Short answer - worth 1 mark)

A

In eukaryotes, the ribosome recognizes the first AUG near the 5’ cap of the mRNA as the start codon. In prokaryotes, the correct AUG is identified by the Shine-Dalgarno sequence upstream of the start codon.

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17
Q

Where is the Shine-Dalgarno sequence located?
a) 3 nucleotides upstream of the AUG codon
b) 10 nucleotides upstream of the AUG codon
c) At the 5’ end of the mRNA

A

b)

18
Q

What is the function of the Shine-Dalgarno sequence?
a) It signals the end of translation.
b) It allows the small ribosomal subunit to bind to the correct AUG start codon.
c) It recruits tRNA to the A-site.

A

b)

19
Q

What part of the ribosome binds to the Shine-Dalgarno sequence?
a) 5S rRNA
b) 16S rRNA in the small subunit
c) 23S rRNA in the large subunit

A

b)

20
Q

What does polycistronic mRNA mean?
a) mRNA that codes for only one protein
b) mRNA that codes for multiple proteins
c) mRNA that is degraded after translation

A

b)

21
Q

Why do eukaryotic mRNAs rarely have polycistronic coding regions?
a) They lack the Shine-Dalgarno sequence.
b) They use polyadenylation instead.
c) Translation initiation is more complex in eukaryotes.

A

c)

22
Q

Where does the ribosome start scanning on eukaryotic mRNA?
a) The poly(A) tail
b) The 5’ cap
c) The first codon

A

b)

23
Q

What happens during leaky scanning?
a) The ribosome skips the first AUG if it lacks the Kozak sequence.
b) The ribosome stops translation prematurely.
c) The ribosome scans mRNA from 3’ to 5’.

A

a)

24
Q

What is the Kozak sequence?
a) A sequence at the 3’ end of mRNA that ends translation
b) A sequence (ACCAUGG) that surrounds the AUG to start translation
c) A poly(A) tail that stabilizes the mRNA

A

b)

25
Q

What modification in Eukarytoes on the mRNA does the small ribosomal subunit recognize first?
a) Poly(A) tail
b) 5’ cap
c) Kozak sequence
d) 3’ cap
e) none of the above

A

b)

26
Q

What are the key differences between translation initiation in prokaryotes and eukaryotes?

a) In prokaryotes, the ribosome binds to the Kozak sequence, while in eukaryotes, it binds to the Shine-Dalgarno sequence.
b) Prokaryotes use the Shine-Dalgarno sequence for ribosome binding, while eukaryotes use the 5’ cap and scanning mechanism.
c) Both prokaryotes and eukaryotes use the 5’ cap structure to identify the AUG start codon.
d) Prokaryotes initiate translation with methionine, while eukaryotes use N-formylmethionine.

A

b)

27
Q

Describe the key differences between translation initiation in prokaryotes and eukaryotes.

A

Prokaryotes: The ribosome binds to the Shine-Dalgarno sequence upstream of the AUG start codon.
Eukaryotes: The ribosome binds to the 5’ cap and scans along the mRNA until it finds the first AUG, usually surrounded by the Kozak sequence.

28
Q

In prokaryotes, what sequence helps the ribosome bind to the correct AUG start codon?
a) Kozak sequence
b) Shine-Dalgarno sequence
c) 5’ cap structure
d) 3’ cap structure
e) Poly A tail

A

b)

29
Q

What mechanism allows eukaryotic ribosomes to locate the correct start codon?
a) Direct binding to AUG
b) Ribosome scanning from the 5’ cap in the 5’ to 3’ direction
c) Recognition of the Shine-Dalgarno sequence

A

b)

30
Q

Why is prokaryotic mRNA often polycistronic?
a) Ribosomes bind to internal AUG codons using Shine-Dalgarno sequences.
b) Ribosomes use scanning to locate multiple AUGs.
c) Translation occurs only at the first AUG.

A

a)

31
Q

Which of the following is not true about eukaryotic mRNA?
a) It contains a 5’ cap structure.
b) It is usually monocistronic.
c) The ribosome binds directly to AUG without scanning.

A

c)

32
Q

Describe two key differences between translation initiation in prokaryotes and eukaryotes.

A

One difference is that in porkaryotic cells the small ribosomal subunit binds directly to the AUG start codon using the SD sequence and in prokaryotes the small ribosomal subunit binds to the mRNA strand by the 5’ cap end.

A secondary key difference would be that in prokarytoes, there is no scanning involved where as in eukaryotes there is ribosome scanning that uses the Kozak sequence to locate the first AUG codon, if no Kozack sequence then this results in leaky scanning where a downstream AUG codon will be selected.

33
Q

Why are post-transcriptional modifications important for tRNA?
a) They increase the size of the tRNA molecule.
b) They stabilize the tRNA structure and help it function properly.
c) They degrade unused tRNAs.

A

b)

34
Q

What percentage of tRNA nucleotides are typically modified?
a) 5%
b) 10%
c) 20%
d) 30 %
e) 15%

A

b)

35
Q

What nucleotide modification results in the formation of inosine?
a) Methylation of uracil
b) Deamination of adenine
c) Addition of sulfur to guanine

A

b)

36
Q

Why is inosine important in the anticodon region of tRNA?
a) It helps the tRNA recognize multiple codons through wobble base pairing.
b) It stops translation.
c) It stabilizes the poly(A) tail.

A

a)

37
Q

What type of base pairing is promoted by post-transcriptional modifications in tRNA?
a) Intermolecular base pairing
b) Intramolecular base pairing
c) Wobble base pairing
d) none of the above

A

b)

38
Q

What enzyme converts uridine into pseudouridine?
a) RNA polymerase
b) Pseudouridine synthase
c) Reverse transcriptase

A

b)

39
Q

Why is pseudouridine important in mRNA vaccines?
a) It destabilizes the RNA to allow faster breakdown.
b) It increases RNA stability and reduces cellular toxicity.
c) It prevents translation of mRNA.

A

b

40
Q

What additional modification was added to pseudouridine for the COVID vaccine?
a) Addition of a sulfur group
b) Addition of a methyl group
c) Addition of an amino group

A

b)

Molecular Biology (11 decks)

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