LSC347 Exam 3 practice Questions and Answers Spring 2026 Arizona State University

This document and all items herein are copyright Pamela A. Marshall and Arizona State University.
This document cannot be shared with anyone or uploaded to any website without prior written
authorization.


LSC 347 Exam 3 Practice

1. The mRNA is read on the ribosome
A. 5’ to 3’
B. 3’ to 5’
C. amino terminus to carboxy terminus
D. carboxy terminus to amino terminus
E. whatever way the ribosome feels that day

2. The polypeptide on the ribosome is made
A. 3’ to 5’
B. 5’ to 3’
C. amino terminus to carboxy terminus
D. carboxy terminus to amino terminus
E. whatever way the ribosome feels that day

3. Which of the following types of repair could NOT be used to repair a thymine dimer?
A. mismatch repair
B. direct repair
C. excision repair
D. homologous recombination repair

4. Chain transfer occurs
A. from the aminoacyl tRNA to the peptidyl tRNA
B. from the peptidyl tRNA to the amino acyl tRNA
C. from the A site to the P site
D. from the P site to the E site
E. none of the above are correct

5. True (A) or False (B) mRNA from prokaryotes will have more than one Shine-Dalgarno sequence if the
mRNA is polycistronic.

6. Which of the following is NOT a mutation that would change a gene sequence?
A. Promoter mutation
B. missense
C. intergenic suppressor
D. frameshift
E. transposon in the gene

7. A repressor mutation affects the Lysine operon. This REPRESSOR PROTEIN always binds to the operator
no matter what. This results in
A. no transcription
B. inducible transcription
C. transcription but no translation
D. no change from wild type
E. constitutive transcription




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, This document and all items herein are copyright Pamela A. Marshall and Arizona State University.
This document cannot be shared with anyone or uploaded to any website without prior written
authorization.



Use the Wobble table and codon table for questions 8 and 9.
Base at 3’ End of mRNA Codon Base at 5’ End of tRNA

U A

G C

C or U G

A or G U

A, U, or C I

Varies Others



8. For the codon for Tyrosine (Tyr), which of the following anticodons would be used? There is only one
correct answer to this question. Think about specificity. 5’UAU3’ 5’UAC3’ are codons
A. 3’UAC5’
B. 5’UAC3’
C. 3’GUU5’
D. 3’AUI5’
E. 3’AUG5’


9. What amino acid is coded for if the anticodon of the tRNA is 5’IAU3’?
A. Ser
B. Tyr
C. Ile
D. Lys
E. Phe


10.At what position in an operon would an attenuator function most effectively?
A. 5' of the transcriptional start site (on the coding strand)
B. 3' of the last gene in the operon (on the coding strand)
C. Between the transcriptional start site and the translational initiation site of the first gene that codes for a
functioning protein
D. Between the -10 and -35 sequences in the promoter
E. In the coding region of any gene in the operon


11. What is antisense RNA in prokaryotes?
A. RNA that makes up the structural component of ribosomes
B. RNA transcript base paired with DNA during transcription elongation
C. RNA transcript that is complementary to an mRNA to bind to the mRNA to inhibit translation
(TRANSCRIBED FROM THE SAME GENE AS THE mRNA)
D. The DNA strand complementary to the template strand
E. RNA transcript that is complementary to an mRNA to bind to the mRNA to inhibit translation
(TRANSCRIBED FROM A DIFFERENT GENE THAN THE mRNA)



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