Deck 16: Protein

Question 1

Describe the central dogma of molecular biology (to do this draw a diagram of the central dogma and describe all the arrows).

Answer 1

Question 2

There is/are ___ start codon(s) and ___ stop codon(s).

A) 1; 1
B) 3; 1
C) 3; 3
D) 1; 3
E) 2; 2

Answer 2

1; 3

Question 3

What do Gln, Asp, and Glu have in common?

A) All are hydrophilic amino acids
B) All have A as the second nucleotide in their codon
C) All have U as the second nucleotide in their codon
D) All have only one codon
E) Both (A) and (B) are correct

Answer 3

Both (A) and (B) are correct

Question 4

The start codon is usually ______.

Question 5

One type of sickle cell anemia is caused by a single point mutation in the hemoglobin gene, in which a glutamic acid is replaced by valine in the final protein. Which of the following codons might result in sickle cell hemoglobin?

A) GAU to GUU
B) GAA to GUA
C) GAG to GAU
D) GUU to GAA
E) CAG to GAG

Question 6

Which of the following represents a DNA mutation in the template strand that would convert serine to cysteine?

A) 5'-GCT-3' to 5'-GCA-3'
B) 5'-AGC-3' to 5'-TGC-3'
C) 5'-AGC-3' to 5'-UGC-3'
D) 5'-AGU-3' to 5'-UGU-3'
E) 5'-TCG-3' to 5'-TCC-3'

Question 7

Which is true of codon wobble?
I. It occurs at codon position 2
II. It can lead to incorrect reading frame
III. It speeds protein synthesis
IV. It can result in weaker H bonding between codon and anticodon

A) I only
B) II and III
C) III only
D) I and II
E) III and IV

Question 8

An open reading frame is defined by _____.

A) a start and stop codon
B) homology with other species
C) placement on a genome map
D) presence of transposable elements
E) absence of highly repetitive sequences

Question 9

What is the similarity between the amino acids that have only one codon each?

A) they are aromatic amino acids
B) they are the sulfur containing amino acids
C) they are neutral polar amino acids
D) they occur very infrequently in proteins
E) none of the above

Question 10

Given the following anticodon, which mRNA codon would pair with it?
5'-IGC-3'

A) '-UCA-3'
B) 5'-UCG-3'
C) 5'-ACU-3'
D) 5'-GUA-3'
E) 5'-GCU-3'

Question 11

Based on the structure shown below, which of the following correctly represents the sequence that would be present at the "XYZ"
Position?

A) UGG
B) TGG
C) CCA
D) Cannot be determined from the given data.
E) None of the above is the correct sequence.

Question 12

The 5' region of mRNA assists with its proper ribosomal placement during initiation of translation. In prokaryotes, the ____ is important for this purpose, while in eukaryotes, the ___ is used.

Question 13

The fidelity of amino acid attachment to a tRNA is enhanced by the ______ ability of the corresponding aatRNA synthetase.

Question 14

Which of the following describes the general three-dimensional structure of a tRNA?

A) a cloverleaf shape with the anticodon and acceptor stem on "leaves" that are opposite each other
B) an L shape with the anticodon at one end of the L and the acceptor stem at the other
C) a large loop with the anticodon and 3' end in very close proximity to each other
D) an elongated cylinder shape with the anticodon and acceptor stem at opposite ends
E) since all tRNAs have very different three-dimensional structures, it is difficult to describe a general shape

Question 15

During the charging of a tRNA, what intermediate is formed?

A) aminoacyl-adenylate
B) aminoacyl-tRNA
C) aminoacyl-ADP
D) tRNA-adenylate
E) none of the above

Question 16

Which of the following explains why the aminoacyl-tRNA synthetase for isoleucine rarely incorporates valine despite the similar structure of these two amino acids?

A) valine does not fit into the binding site for isoleucine
B) only leucine and isoleucine can fit in the active site of the enzyme
C) before incorporation, the enzyme methylates valine to make it into an isoleucine
D) the enzyme contains a proofreading site that removes valine from the tRNA
E) none of the above

Question 17

What type of bond connects the tRNA with its amino acid (AA)?

A) ester between AA carboxylate and tRNA 3' hydroxyl
B) mixed anhydride of AA carboxylate and tRNA 3'phosphate
C) phosphoramide of AA amine and tRNA 3'phosphate
D) mixed anhydride of AA carboxylate and tRNA 5' phosphate
E) phosphoramide of AA amine and tRNA 5' phosphate

Question 18

Use the structure below to answer the following questions

-Where is the anticodon in the following structure?

A) 1
B) 2
C) 3
D) 4
E) 5

Question 19

Use the structure below to answer the following questions

-The D loop is represented by

A) 1
B) 2
C) 3
D) 4
E) 5

Question 20

Use the structure below to answer the following questions

-The amino acid would be attached to this structure at

A) 1
B) 2
C) 3
D) 4
E) 5

Question 21

Approximately what fraction of the mass of a ribosome is due to protein?

A) 1/2
B) 1/3
C) 1/4
D) 1/5
E) 1/6

Question 22

Class I and Class II aminoacyl-tRNA synthetases differ in
I. their major structures
II. the general size of aa that fits their active sites
III. exposure of their active sites
IV. fidelity in proofreading

A) I only
B) I and III
C) I, III and IV
D) II, III and IV
E) I, II and III

Question 23

The selectivity of aminoacyl-tRNA synthetases can be explained by

A) the strength of even weak interactions of the amino acid within its catalytic binding site
B) the topography of the enzymes' proofreading sites
C) recognition of the anticodon loop only
D) specific cations found in the catalytic binding site
E) Both (A) and (B) are correct

Question 24

In the ribosome, interactions among the varied RNA molecules include

A) mRNA and rRNA
B) tRNA and mRNA
C) tRNA and rRNA
D) all of the above
E) none of the above

Question 25

Which protein(s) important to translation can be considered guanine nucleotide exchange factors?
I. eIF2
II. eIF3
III. EF-G
IV. EF-Tu

A) I and II
B) III and IV
C) I, III and IV
D) II and III
E) IV only

Question 26

Which amino acid is the first incorporated into a prokaryotic protein?

A) N-formylthreonine
B) N-formylmethionine
C) N-formylaspartate
D) N-formylglutamine
E) N-formylcysteine

Question 27

What sequence is located about 10 bases upstream of the initiation codon?

A) Watson-Crick sequence
B) Meselson-Stahl sequence
C) Hershey-Chase sequence
D) Avery-MacLeod sequence
E) Shine-Dalgarno sequence

Question 28

What two elements of translation are paired by a Shine-Dalgarno sequence?

A) initial tRNA with the initiation codon
B) initial tRNA with the ribosomal A site
C) mRNA with 23S rRNA of the ribosome
D) mRNA with 16S rRNA of the ribosome
E) mRNA with initial tRNA

Question 29

In E. coli translation, _____ aids with binding of the fMet-tRNA to the 30S subunit while _____ blocks the A site.

A) IF-1; IF-2
B) IF-1; IF-3
C) IF-2; IF-1
D) IF-2; IF-3
E) IF-3; IF-1

Question 30

How is the initiation codon found in eukaryotic translation?

A) a sequence similar to the Shine-Dalgarno sequence is located
B) the 5'cap binds just beyond the P site of the ribosome
C) the fMet-tRNA is able to locate the initiation codon before binding to the ribosome
D) when the mRNA circularizes, the poly(A) tail enables location of the initiation codon
E) the first AUG codon is found when the 40S subunit scans the mRNA from the 5' end

Question 31

The first elongation event is

A) the formation of the first peptide bond, when the amino N of amino acid 2 attacks the carboxyl C of methionine
B) the formation of the first peptide bond, when the amino N of methionine attacks the carboxyl C of amino acid 2
C) binding of eIF-2 or IF-2 to amino acid 2
D) translocation of the ribosome to place empty tRNAmet into the E site
E) binding of EF-G to tRNA-amino acid 2

Question 32

Within the ribosome during translation, the growing polypeptide chain is always attached to

A) tRNAmet
B) the tRNA held in the E site after translocation
C) the tRNA held in the E site before translocation
D) the tRNA held in the P site after translocation
E) the tRNA held in the A site after translocation

Question 33

Hydrolysis of GTP by EF-Tu is thermodynamically required for _____.

A) proofreading
B) transpeptidation
C) translocation
D) aminoacyl-tRNA binding to the ribosomal A site
E) none of the above

Question 34

Polypeptide synthesis proceeds from the _____ to the _____.

A) entrance site; exit site
B) 50S subunit; 30S subunit
C) C-terminus; N-terminus
D) N-terminus; C-terminus
E) peptidyl site; aminoacyl site

Question 35

Which diagram depicts correctly a ribosome engaged in translation?

A) a
B) b
C) c
D) d

Question 36

EF-G is required for _____ as it binds to the ribosome in a manner similar to _____.

A) translocation; the EF-Tu-tRNA complex
B) transpeptidation; the EF-Tu-GDP complex
C) transferase; an uncharged tRNA
D) transduction; an aminoacyl-tRNA
E) none of the above

Question 37

Translation termination requires ______ that recognize Stop codons.

Question 38

Translation termination

A) in prokaryotes requires a single release factor RF-1, which is also a GTPase
B) in eukaryotes requires a single release factor eRF-1
C) in eukaryotes requires one of three release factors: RF-1, RF-2 or RF-3
D) none of the above

Question 39

Which is NOT true of protein translation?

A) About 10% of cell proteins are completely synthesized and reside in the cytosol.
B) A single mRNA in the cytosol may have multiple ribosomes translating it at the same time.
C) Ribosomes that reside permanently on the rough ER translate only proteins destined for secretion from the cell.
D) Nascent proteins with a signal peptide at their amino terminus bind a signal recognition particle that binds an ER receptor.
E) Polysomes are multiple ribosomes translating the same mRNA.

Question 40

In eukaryotic cells, when a protein is to be translocated to the endoplasmic reticulum, what must occur for complete translation to occur?

A) the N-terminus binds SRP which delivers the ribosome and growing peptide to the ER
B) the N-terminus binds SRP which is then partially cleaved by a signal peptidase
C) the ribosome must be translocated into the ER prior to initiation of translation
D) the ribosome must be bound to the ER before translation begins
E) a chaperone protein embedded in the ER membrane binds the N-terminus

Question 41

Which of the following aids in protein folding by completely sequestering a polypeptide from its environment?

A) ubiquitin
B) trigger factor
C) chaperonin
D) heat shock protein
E) signal recognition particle

Question 42

Chaperones such as GroEL and GroES generally bind to what regions of a polypeptide?

A) hydrophobic regions
B) acidic regions
C) basic regions
D) both acidic and basic regions
E) neutral polar regions

Question 43

Which of the following antibiotics mimics an aminoacyl-tRNA?

A) chloramphenicol
B) erythromycin
C) penicillin
D) puromycin
E) streptomycin

Question 44

Erythromycin

A) is specific for bacteria because it binds preferentially to the 50S ribosomal subunit, which is prokaryote-specific
B) is specific for bacteria because it binds preferentially to the 40S ribosomal subunit, which is prokaryote-specific
C) causes early termination of bacterial protein translation because it is an analog of release factor 3
D) causes early termination of bacterial protein translation because it is an analog of EF-Tu and translocation ceases
E) is not naturally-occurring

Question 45

Which is NOT true of lectins such as ricin?

A) They are naturally occurring, commonly from plants
B) They are proteins that bind carbohydrates
C) They block protein synthesis in prokaryotes by binding to the 16S subunit of the ribosome
D) They depurinate ribosomal RNAs in prokaryotes
E) They are endoglycosylases that target ribosomal adenines