The Genetic Code and Translation
1. All proteins are made up of some combination of 20 essential amino acids. (F)
2. Like nucleic acids, polypeptides have polarity (T)
3. The primary sequence of the protein determines the quaternary structure of a
4. During translation initiation, the initiator tRNAmet binds to the P site of a
6. The codon for methionine appears only at the beginning of the mRNA for a
protein, not in the middle or in the end. (F)
7. The first three bases at the 5′ end of an mRNA are the AUG at which
translation begins. (F)
8. Ribosomes move along an mRNA in the 5′ to 3′ direction. (T)
9. A special tRNA that does not have an attached amino acid binds to stop
codons to terminate translation. (F)
10. UGG is an example of a stop codon. (F)
11. In eukaryotes, the 5′ cap and the 3′ poly(A) tail are involved in translation
12. An mRNA can be translated by only one ribosome at a time. (F)
13. Because there is no nucleus in a prokaryote, the 5' end of an mRNA can be
translated while the 3′ end is still being transcribed. (T)
Fill in the Blank
Use this diagram for questions 14-18.
| | | | |
| G| G G T C C A| |
5′ A C 3′
14. Process 2 is translation.
15. If the bottom strand of the DNA (sequence not shown) is the template, the
RNA sequence, left to right 5′ to 3′, is AGGGUCCAC.
16. If the bottom strand of the DNA is the template, the protein amino acid
sequence from the RNA is arg-val-his.
17. If the bottom strand of the DNA is the template, the tRNA anticodon
sequence, left to right 5′ to 3′, for the first RNA codon is CCU.
18. During initiation, the small subunit is the first part of the ribosome to
associate with the mRNA.
19. During elongation, an incoming charged tRNA enters at the A site of the
20. Codons that specify the same amino acid are said to be synonymous.
21. The amino acid sequence of a polypeptide is referred to as the primary
sequence of the polypeptide.
The Genetic Code and Translation
22. There are 64 different codons, which encode 20 amino acids and 3 stop
Use the following diagram for questions 25-26. Solid circles represent amino
23. The next step in the translation of this mRNA will be the formation of a
peptide bond between which two amino acids?
*a. amino acid 2 and amino acid 3
b. amino acid 2 and amino acid 4
c. amino acid 1 and amino acid 3
d. amino acid 1 and amino acid 2
24. After the peptide bond forms, what will happen?
a. tRNA A will be carrying the polypeptide and it will shift to the P site.
b. tRNA A will be carrying the polypeptide and it will shift to the A site.
*c. tRNA B will be carrying the polypeptide and it will shift to the P site.
d. tRNA B will be carrying the polypeptide and it will shift to the A site.
25. What is the function of peptidyl transferase activity?
a. It charges tRNAs.
b. It acetylates the end of a protein after translation.
c. It cleaves the polypeptide from the last tRNA during termination.
d. It moves ribosomes along mRNA during translation.
*e. It forms peptide bonds.
26. A tRNA anticodon is 5′ICG3′. What amino acid does it carry?
28. To translate a mRNA you require two other RNAs. These are
a. tRNA and mRNA.
b. tRNA and miRNA.
*c. tRNA and rRNA.
d. rRNA and siRNA.
29. The genetic code is said to be “degenerate” because
*a. there are more codons than amino acids.
b. there are more amino acids than codons.
c. different organisms use different codons to encode the same amino acid.
d. some codons specify more than one amino acid.
30. The genetic code is universal except for
a. prokaryotes, which use a different genetic code than eukaryotes.
*b. a few mitochondrial genes, which substitute one sense codon for another.
c. viruses, which use an entirely different genetic code.
d. archaebacteria, which have their own genetic code.
31. The function of aminoacyl-tRNA synthetases is to
a. transcribe tRNA genes.
b. match tRNA anticodons and mRNA codons at the ribosome.
*c. attach amino acids to tRNAs.
d. form the peptide bond between amino acids at the ribosome.
33. When codons that code for the same amino acid differ in their ________, a
single tRNA might bind both of them through wobble base pairing.
a. 5′ base
b. middle base
*c. 3′ base
34. An mRNA has the codon 5' UAC 3'. What tRNA anticodon will bind to it?
a. 5′ AUG 3′
*b. 3′ AUG 5′
c. 5′ ATC 3′
d. 3′ ATC 5′
35. An mRNA has the stop codon 5'UAA3'. What tRNA anticodon will bind to it?
c. 5″ ACU3′