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Quick Biochemistry - Nucleic Acids (Section 8)

1
Which type of tRNA initiates translation in eukaryotic cells?
Answer
(A)
Mehtionyl tRNA
2
Which tRNA starts translation in prokaryotic cells?
Answer
(B)
Formylmethionyl tRNA
3
In eukaryotic cells, which initiation factor is NOT a part of the 40S pre-initiation complex?
Answer
(D)
elF-4
4
To which cellular component do the eukaryotic initiation factors 4A, 4B, and 4F bind?
Answer
(C)
mRNA
5
What is the specific codon that signals the start of translation?
Answer
(A)
AUG
6
In association with which factor(s) does the initial amino acyl tRNA approach the 40 S ribosomal subunit?
Answer
(B)
elF-2 and GTP
7
What is the primary function of elF-1A and elF-3?
Answer
(D)
To prevent binding of 60 S subunit to 40 S subunit
8
Which enzymatic activity is associated with elF-4 A?
Answer
(A)
ATPase activity
9
What is the primary function of elF-4 B?
Answer
(D)
Unwinds mRNA near its 5' end
10
Where is peptidyl transferase activity found?
Answer
(B)
60 S ribosomal subunit
11
Following the creation of a peptide bond, what is responsible for moving mRNA along the ribosome?
Answer
(B)
eEF-2 and GTP
12
Which of the following substances prevents formylmethionyl tRNA from attaching to the 30S ribosomal subunit in prokaryotes?
Answer
(A)
Streptomycin
13
What is the effect of tetracyclines on the binding of amino acyl tRNAs?
Answer
(A)
30 S ribosomal subunits
14
Which substance interferes with the peptidyl transferase function of 50S ribosomal subunits?
Answer
(C)
Chloramphenicol
15
What is the effect of erythromycin's binding to the 50S ribosomal subunit?
Answer
(C)
Inhibits translocation
16
In which type of cell does puromycin trigger early chain termination?
Answer
(C)
Both (A) and (B)
17
Which process is disrupted by diphtheria toxin?
Answer
(D)
Eukaryotic EF-2
18
Which of the following is NOT a characteristic of proteins that are secreted from a cell?
Answer
(D)
They are tagged with ubiquitin
19
Where are the SRP receptors involved in protein export located?
Answer
(B)
Endoplasmic reticulum
20
At what point is the signal sequence removed from proteins?
Answer
(B)
In the endoplasmic reticulum
21
What determines how long a protein lasts?
Answer
(B)
N-terminus amino acid
22
In addition to the protein-coding genes, what other sequences are found in DNA that control gene regulation?
Answer
(C)
Cis-acting elements
23
What are inducers and repressors classified as?
Answer
(B)
Trans-acting factors
24
Which of the following is a cis-acting element?
Answer
(D)
Silencers
25
What is the main function of silencer elements?
Answer
(C)
Decrease the expression of some structural genes
26
Which of the following are examples of trans-acting factors?
Answer
(B)
Repressors
27
Which of the following is NOT a characteristic of enhancer elements?
Answer
(B)
Each enhancer activates a specific promoter
28
What might cause the dihydrofolate reductase gene to be amplified?
Answer
(D)
Amethopterin
29
What structural motif is commonly found in proteins that influence transcription by interacting with DNA?
Answer
(D)
All of these
30
Where is the Lac operon, a collection of genes, found?
Answer
(B)
E. coli
31
What is the composition of the lac operon?
Answer
(D)
A regulatory gene, an operator, a promoter and three structural genes
32
The regulatory i gene of the lac operon performs which function?
Answer
(D)
Is always expressed
33
Where does the RNA polymerase holoenzyme bind within the lac operon?
Answer
(D)
Promoter region
34
Which factor prevents the transcription of the z, y, and a genes in the lac operon?
Answer
(C)
Repressor
35
What prevents the transcription of the structural genes in the lac operon through the binding of the repressor tetramer?
Answer
(B)
Operator locus
36
The enzymes produced by the z, y, and a genes of the lac operon are activated by which substance?
Answer
(B)
Allo-lactose
37
What promotes the binding of RNA polymerase holoenzyme to the promoter region of the lac operon?
Answer
(C)
CAP-CAMP complex
38
How do lactose and its analogs positively regulate the lac operon?
Answer
(D)
Binding to repressor subunits so that the repressor cannot attach to the operator locus
39
Which of the following does NOT affect the expression of structural genes in the lac operon?
Answer
(C)
cAMP
40
Which components are coded for in the lac operon's coding sequences?
Answer
(D)
i, z, y and a genes
41
What is a potential cause of genetic alterations?
Answer
(C)
Alkylating agents
42
What compound is capable of inducing mutations?
Answer
(D)
All of these
43
What is the effect of nitrosamine on a specific DNA base?
Answer
(A)
Cytosine to form uracil
44
Which alteration can occur in DNA due to ultraviolet radiation exposure?
Answer
(C)
Thymine dimers
45
How can DNA damage caused by ultraviolet radiation be fixed?
Answer
(D)
All of these
46
What is the underlying defect in Xeroderma pigmentosum?
Answer
(A)
uvr ABC excinuclease
47
Which of the following does NOT accurately describe Xeroderma pigmentosum?
Answer
(B)
Its inheritance is autosomal dominant
48
What type of mutation involves replacing adenine with guanine in DNA?
Answer
(B)
Transition
49
What type of mutation involves replacing thymine with adenine in DNA?
Answer
(C)
Transversion
50
What describes a point mutation's origin?
Answer
(A)
Substitution of a base