Chapter 13 Translation Flashcards
(43 cards)
1) A bacterium's large subunit is 60S and its small subunit is 40S. What is the size of the ribosome containing both subunits? A) 20S B) 100S C) 70S D) 120S E) 80S
E
2) Which of the following is true regarding the tRNA structure?
A) The tRNA binds to an mRNA’s codon at the variable loop.
B) An amino acid binds to the 5′ end of the tRNA molecule.
C) A tRNA molecule that has an amino acid attached to it is called a charged tRNA.
D) The nucleotides found in a tRNA molecule can only be adenine, uracil, guanine, and cytosine.
E) The anticodon is found at the 3′ end of the tRNA molecule.
C
3) If humans had 25 amino acids instead of 20 amino acids then how many aminoacyl tRNA synthetases would humans have? A) 4 B) 25 C) 75 D) 20 E) 3
B
4) During initiation in bacterial translation, a particular mutation causes the premature binding of the large ribosome subunit to the small ribosome subunit. Which component of initiation is not
working properly?
A) IF3 B) Shine-Dalgarno sequence on the mRNA C) Ribosome's E site D) IF2 E) IF1
A
5) A mutation in EF-Tu would have a DIRECT effect on which part of translation?
A) The peptide bond formation would be blocked.
B) The polypeptide would form, but translation termination would be blocked.
C) The small and large subunits would not bind.
D) Translocation would be directly blocked.
E) The next tRNA would not be able to enter the A site of the ribosome.
E
6) What signals termination of translation in bacteria?
A) EF-Tu and EF-G
B) a tRNA specific to the stop codon enters the ribosome’s A site
C) ribozymes
D) the stop amino acid is attached to the growing peptide chain
E) RF1 and RF2
E
7) A protein is 300 amino acids long. Which of the following could be the number of total nucleotides in the section of DNA that codes for this protein? (Remember: DNA is double-stranded.) A) 3 B) 900 C) 300 D) 100 E) 1800
E
8) The term peptidyl transferase relates to ________.
A) discontinuous strand replication
B) elongation factors binding to the large ribosomal subunit
C) 5′ capping of mRNA
D) peptide bond formation during protein synthesis
E) base additions during mRNA synthesis
D
9) X-ray crystallography has revealed and confirmed many details about the ribosome. All of the following are such details, EXCEPT ________.
A) rRNA in the ribosome is in direct contact with the different loops of the tRNA molecule
B) rRNAs are more likely than proteins to be the catalytic molecule of the ribosome
C) the wobble hypothesis is further supported
D) the ribosome is a dynamic structure that changes during its different functional states
E) the distance the tRNA must travel between the E, P, and A sites is considered to be relatively
short
E
10) Translation in bacterial and eukaryotic cells has many similarities, but there are also several key differences. Which of the following is one of those differences that is seen in eukaryotes?
A) Eukaryotic ribosomes are smaller with fewer proteins and RNA molecules.
B) Translation and transcription are coupled.
C) Eukaryotes only require one release factor that recognizes all three stop codons.
D) Eukartyotic mRNA contains a Shine—Dalgarno sequence that increases the efficiency of translation.
E) Eukaryotes use the 5′ G-cap and Poly-A-tail on their mRNAs to initiate translation.
E
11) The one-gene:one-enzyme hypothesis emerged from work on which two organisms? A) Drosophila and humans B) Neurospora and Drosophila C) E. coli and yeast D) E. coli and humans E) All of the answers listed are correct
B
12) By their experimentation using the Neurospora fungus, Beadle and Tatum were able to propose the far-reaching hypothesis that ________.
A) genetic recombination occurred in Neurospora
B) the role of a specific gene is to produce a specific enzyme
C) more than one codon can specify a given amino acid
D) several different enzymes may be involved in the same step in a biochemical pathway
E) prototrophs will grow only if provided with nutritional supplements
B
13) A researcher is studying the synthesis of a specific amino acid found in Neurospora. She knows that the pathway begins with a precursor that is converted into the amino acid with two known
intermediates (Substance Blue and Substance Green). She accurately predicts that this amino acid synthesis pathway is catalyzed by three enzymes, (I, II, and III). She subsequently identifies three mutants that she calls Mutant I, Mutant II, and Mutant III. With the information about the mutants below place the enzymes in the order that the enzymes act in this pathway. (Note: the numbers I, II, and III don’t necessarily indicate the order in which the enzymes appear.)
Mutant I (only Enzyme I is mutated) is unable to synthesize the amino acid even if she provided the mutant with both Substance Blue and Substance Green.
Mutant II (only Enzyme II is mutated) is able to synthesize the amino acid if she provided the mutant with Substance Blue or Substance Green.
Mutant III (only Enzyme III is mutated) is able to make the amino acid if she provided the mutant with Substance Green, but not if she provided the mutant with only Substance Blue.
A) I, II, III
B) II, III, I
C) II, I, III
D) III, I, II
E) III, II, I
F) More than one codon can specify a given amino acid.
B
14) The β chain of adult hemoglobin is composed of 146 amino acids of a known sequence. In comparing the normal β chain with the β chain in sickle-cell hemoglobin, what alteration is one likely to find?
A) valine instead of glutamic acid in the sixth position
B) glutamic acid replacing valine in the first position
C) frameshift substitutions
D) trinucleotide repeats
E) extensive amino acid substitutions
A
15) Often point mutations can cause a protein to be made that differs in just one amino acid. Which of the following changes is most likely to cause the greatest change in protein function?
A) a mutation that replaces a serine with a cysteine
B) a mutation that replaces a valine with an isoleucine
C) a mutation that replaces a glutamic acid with an aspartic acid
D) a mutation that replaces an asparagine with a glutamine E) a mutation that replaces a proline with an aspartic acid
E
16) The primary structure of a protein is determined by ________.
A) the sequence of amino acids
B) hydrogen bonds formed between the components of the peptide linkage C) pleated sheets
D) a series of helical domains
E) covalent bonds formed between fibroin residues
A
17) The protein shown below provides an example of which level of protein folding?
A) tertiary B) quaternary C) primary D) pentenary E) secondary
B
18) Side groups of amino acids are typically classified under which of the following? A) primary, secondary B) linear, circular C) alpha, omega D) polar, nonpolar E) long, short
D
19) All of the following are examples of posttranslational modifications, EXCEPT________.
A) Polypeptide chains can be cleaved to produce a shorter and functional polypeptide.
B) The N-terminal amino acid is often removed or modified.
C) Individual amino acid residues are sometimes modified, such as adding a phosphates, acetyl,
or methyl groups can be added.
D) Polypeptides can be degraded and then reassembled to produce entirely different sequenced
polypeptides.
E) Prosthetic groups, such as metals or vitamins, can be added.
D
20) What is the name of the protein that helps fold other proteins into their final and functional form? A) flippase B) chaperone C) proteasomes D) ubiquitin E) collagen
B
21) Creutzfeldt-Jakob, Huntington, Alzheimer, and Parkinson disease are all characterized with which part of protein synthesis? A) initiation B) N-terminal modification C) termination D) elongation E) protein folding
E
22) Which protein class directly controls many of the metabolic reactions within a cell? A) operator proteins B) hydrophilic proteins C) structural proteins D) enzymes E) repressor proteins
D
23) Modular portions of a protein that fold into stable conformations with specific functional capabilities are referred to as \_\_\_\_\_\_\_\_. A) protein subunits B) protein chaperones C) protein quaternary structures D) protein secondary structures E) protein domains
E
24) Describe the structure of a tRNA molecule. Your answer should include a list of five important sites on the tRNA and two reasons why tRNA’s modified bases are important.
The five sites are amino acid binding site, ΤψC stem, variable loop, anticodon stem, D stem, and acceptor stem. The modified bases are important in conferring structural stability and play a role in hydroben bonding between tRNA and
mRNA, which helps explain the wobble effect.
