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Biochemistry Session 1 - Genes to Proteins

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Biochemistry Quiz on Biochemistry Session 1 - Genes to Proteins, created by Kathleen Lonergan on 06/06/2019.
Kathleen Lonergan
Quiz by Kathleen Lonergan, updated more than 1 year ago
Kathleen Lonergan
Created by Kathleen Lonergan about 5 years ago
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Resource summary

Question 1

Question
What is "the central dogma?"
Answer
  • DNA is transcribed to RNA which is translated into proteins.
  • DNA is translated to RNA which is transcribed into proteins.
  • RNA is transcribed to DNA which is translated into proteins.
  • RNA is translated to DNA which is transcribed into proteins.

Question 2

Question
Which of the following terms accurately describes all of the proteins translated from functional mRNA transcripts in a given cell?
Answer
  • Exome
  • Transcriptome
  • Proteome
  • Metabolome

Question 3

Question
The human genome is over six feet long and includes 23,000 coding genes. What percentage of intact human DNA actually codes for an expressible protein product?
Answer
  • 3-4%
  • 1-2%
  • 6-7%
  • 10-12%

Question 4

Question
The exome is the RNA component remaining after processing, editing, and splicing together __________ from the original primary transcript of RNA derived from DNA. The intervening sequences are called __________.
Answer
  • exons, introns
  • codons, base pairs
  • introns, exons
  • base pairs, codons

Question 5

Question
Proteins need to interact with specific DNA sequences for a variety of reasons. ____________ access specific DNA base-pairing sequences through the ___________ groove. General interactions with DNA occur with the general structural motif of DNA through the ___________ groove. Positively charged amino acids in __________ proteins interact with the negatively charged DNA phosphoribosyl backbone.
Answer
  • Histones, major, minor, transcription factor
  • Histones, minor, major, transcription factor
  • Transcription factors, minor, major, histone
  • Transcription factors, major, minor, histone

Question 6

Question
The DNA double helix consists of two anti-parallel DNA strands. Which of the following properties listed are responsible for the double helix's stable structure? (Select all that apply)
Answer
  • Hydrogen bonds
  • Resonance stabilization
  • Covalent bonds linking the two strands
  • Each strand's phosphodiester backbone

Question 7

Question
Histones come together to form an octomer that is the core of a complex called the nucleosome. Nucleosomes are essential to binding and stabilizing DNA. DNA wrapped around a nucleosome core forms the fundamental unit of __________.
Answer
  • Chromosomes
  • Chromatid
  • Chromatin
  • Solenoids

Question 8

Question
Transcription factors are effectively competing for specific DNA sequence binding sites, establishing a protein complex on the DNA that is promoting gene expression. This is most likely describing which chromatin modification?
Answer
  • Euchromatin
  • Heterochromatin
  • Chromatid

Question 9

Question
Which of the following is an example of an irreversible reaction that would block the electrostatic interactions between a histone and the phosphoribosyl backbone of DNA, ultimately leading to reduced nucleosome affinity to DNA?
Answer
  • Histone methylation
  • Histone acetylation
  • DNA methylation
  • DNA acetylation

Question 10

Question
Cell signaling has activated the histone acetyl transferase (HAT) mechanism. What could we expect to observe? (Select all that apply)
Answer
  • Acetylation of histone proteins
  • Deacetylation of histone proteins
  • Elevated levels of local gene expression
  • Inactive gene expression
  • Promoter site exposure by a remodeling engine

Question 11

Question
Which of the following could lead to silencing gene expression in DNA?
Answer
  • HDAC activation
  • Z-DNA structural conformation
  • Chromatin condensation
  • Hypermethylated meCG regions

Question 12

Question
You are observing a cell and notice transcription and translation are occurring at the same time. This could be a(n) __________ cell. (Select all that apply)
Answer
  • Protist
  • Plant
  • Bacterial
  • Animal

Question 13

Question
The lactose operon codes for one polycistronic mRNA. Which of the following would NOT result in the expression of this operon?
Answer
  • Allolactose binding with the repressor protein.
  • The spontaneous conversion of lactose to allolactose.
  • Readily available glucose.
  • Sigma factor binding to its promoter element.

Question 14

Question
Which of the following is NOT a cis-element?
Answer
  • TATA box
  • Enhancer
  • Silencer
  • Sigma factors

Question 15

Question
On this lac operon, what does "o" bind to?
Image:
Picture1 (binary/octet-stream)
Answer
  • Sigma factor
  • mRNA
  • Repressor protein
  • Promoter element

Question 16

Question
In a eukaryotic cell, signal transduction networks are triggered by environmental influence. Which of the following is true regarding the activation of trans-elements and the induction of gene expression?
Answer
  • Transcription factors are already active in the cytosol and require no further intervention to promote gene expression.
  • Modification of an inhibitory protein would cause it to activate and bind to a transcription factor, rendering the TF inactive.
  • Transcription factors assemble on enhancer regions to recruit chromatin remodeling complexes.
  • Transcription factors can be activated by direct phosphorylation.

Question 17

Question
Neurotransmitters, hormones, growth factors, and environmental stimuli can all activate various signal transduction networks, thereby controlling different specific sets of genes. The CRE-CREB transcription factor is an example of one of these signal transduction networks. Protein kinase, PKA, can play a major role in the expression of this transcription factor. Which of the following best describes how PKA influences this pathway?
Answer
  • PKA phosphorylates numerous targets, including CREB, causing a conformational change that induces the assembly of a transcriptional complex.
  • PKA stimulates adenylate cyclase to synthesize cyclic-AMP.
  • PKA binds to a receptor on the cell surface, causing a change in receptor conformation.
  • PKA does not influence this pathway, it is an inhibitor.

Question 18

Question
There are various mechanisms by which transcription can be initiated. Which of the following involves denaturing DNA in and around the promoter and open reading frame?
Answer
  • Closed promoter interaction
  • Closed to open DNA transition
  • Open promoter - RNA polymerase initiation
  • Elongation

Question 19

Question
Which of the following is NOT required for the RNA polymerase reaction mechanism?
Answer
  • Mg+2
  • -OH group
  • Ca+2
  • 4 NTP

Question 20

Question
During elongation of an RNA transcript, RNA and DNA form a complex in the active site. Which of the following most appropriately describes this complex?
Answer
  • It consists of the DNA coding strand and the nascent RNA.
  • It does not rotate during elongation.
  • It is approximately two turns of an A-type nucleic acid double helix.
  • It consists of the DNA template strand and the nascent RNA.

Question 21

Question
Transcriptional termination can be protein dependent. Which of the following are true regarding rho protein dependent termination? (Select all that apply)
Answer
  • This method involves the formation of a rho hexameric complex.
  • This method uses ATP to roll along the RNA strand.
  • This method involves cleaving the nascent RNA strand prior to contacting the RNA polymerase complex.
  • This mechanism is assisted by the formation of secondary structures in the nascent RNA strand that slow the procession rate of RNA polymerase.

Question 22

Question
The formation of a secondary structure that blocks the exit channel in RNA polymerase, ultimately causing stress and shearing the DNA-RNA heteroduplex in the active site, is indicative of what type of transcription termination?
Answer
  • RNA sequence-structure dependent, common in eukaryotes
  • RNA sequence-structure dependent, common in prokaryotes
  • Rho protein dependent, common in eukaryotes
  • Rho protein dependent, common in prokaryotes

Question 23

Question
If you accidentally ingested an amanita phalloides mushroom containing 2 uM alpha-amanitin - what could you expect to happen? (Select all that apply)
Answer
  • mRNA synthesis would stop
  • tRNA synthesis would stop
  • Inhibition of RNApol III
  • Death

Question 24

Question
Transcription in eukaryotes is a compartmentalized process. Which of the following processes would you expect to see in the nucleus?
Answer
  • mRNA editing
  • RNA degradation
  • RNA processing
  • RNA silencing
  • rRNA and tRNA post-transcriptional modifications

Question 25

Question
The 3'-polyA tail is found in over 80% of all eukaryotic _________.
Answer
  • mRNAs
  • tRNAs
  • rRNAs
  • DNA

Question 26

Question
Which of the following is NOT true regarding the 5'-cap structure added to the mRNA transcript?
Answer
  • The cap is added almost as soon as the nascent strand of RNA streams out of the RNA polymerase complex.
  • The cap masks the strand from exonuclease degradation, improving half-life and stability.
  • The cap has no significant role in translation.
  • The cap is tightly bound by cap-recognition proteins.

Question 27

Question
RNA splicing is a key editing mechanism that removes introns from the primary transcript. This mechanism is dependent on the formation of a stable complex called a spliceosome. Which of the following is NOT correct regarding the functional units of the spliceosome?
Answer
  • There must be at least 5 snRNPs present to form the complex.
  • The U1 snRNP binds to the donor 5' splice site.
  • The U2 snRNP binds to the acceptor 3' splice site.
  • The U4, U5, and U6 snRNPs associate and form a stable complex.

Question 28

Question
Which of the following sequences contains splicing information that ensures accurately assembled final processed mRNA and is the source of various important regulatory small RNA fragments generated during processing?
Answer
  • Exons
  • Introns
  • Codons
  • Spliceosome

Question 29

Question
If splice site sequences are mutated, exon skipping may occur. What is another reason splicing may not occur accurately?
Answer
  • The spliceosome is assembled in a kinetic fashion as RNA emerges from the RNA polymerase complex.
  • Protein factors bound to the splicing enhancer or silencer elements of the intron expose the splicing site for a snRNP to bind.
  • Protein factors bound to the splicing enhancer or silencer elements of the intron affect the overall stability of the spliceosome.
  • There are no other reasons splicing would occur inaccurately.

Question 30

Question
Tropomyosin has a primary RNA transcript of 11 exons. Which of the following processed transcripts can result from tropomyosin's primary transcript?
Answer
  • Striated muscle
  • Smooth muscle
  • Liver
  • Brain

Question 31

Question
UAA, UAG, and UGA are stop codons on mRNA strands that signal the cessation of translation. Why does this mechanism occur?
Answer
  • RNA polymerase does not recognize stop codons, stopping translation.
  • There are no tRNAs to accommodate these sequences, stopping translation.
  • The amino acids these sequences code for have a chemical structure that conformationally changes the mRNA, stopping translation.
  • The tRNAs that accommodate these sequences react with the mRNA and break the amino acid chain.

Question 32

Question
What molecule is used to charge a specific amino acid to a specific tRNA?
Answer
  • ATP
  • GTP
  • cAMP
  • GMP

Question 33

Question
Looking at a newly synthesized polypeptide that has not been edited, what amino acid must appear at the end?
Answer
  • Methionine
  • Serine
  • Glycine
  • Glutamine

Question 34

Question
Select all that apply regarding the genetic code.
Answer
  • The genetic code is a continuous set of triplets from start to finish.
  • The genetic code is degenerate. There may be more than one codon that codes for any single amino acid, but there is never more than one amino acid per unique codon.
  • The genetic code is subdivided into codon groups.
  • The genetic code contains one unique start codon and five unique stop codons.

Question 35

Question
Which of the following enzymes attaches specific amino acids to the 3' end of cognate tRNA strands?
Answer
  • Aminoacyl tRNA synthetase
  • DNA synthetase
  • Protease
  • RNA polymerase

Question 36

Question
Which of the following options helps to maintain the genetic code during translation? (Select all that apply)
Answer
  • The quick reversal of mis-acylations by an accurate editing site immediately adjacent to the amino acylation site.
  • Highly specific interactions between protein and tRNA
  • The unique aminoacyl tRNA synthetases that correspond to their individual tRNA strands
  • Rho protein modification

Question 37

Question
Which of the following is representative of a typical eukaryotic ribosome?
Answer
  • Three subunits - 120S complex
  • Two subunits - 80S complex
  • One subunit - 60S complex
  • Two subunits - 60S complex

Question 38

Question
What is the first step of prokaryotic initiation of translation?
Answer
  • Initiation complex IF-2-GTP-fmet-TRNAi scans mRNA. Interaction between the 16S rRNA and Shine-Delgarno sequence is established, binding the initiator complex tightly to the mRNA.
  • Initiation factors IF-1 and IF-3 bind to the 30S subunit, forcing dissociation.
  • IF-2-GTP-fmet-tRNAi complex and mRNA bind to the 30S subunit, forming an initiation complex.
  • Strong 16S rRNA to mRNA interaction places fmet-tRNAi in an AUG initiation site.

Question 39

Question
The protein elongation cycle in prokaryotes is defined by three distinct sites located on the ribosome: A, P, and E. What is the main function of the E site?
Answer
  • Binding incoming aminoacyl tRNA
  • Holding the peptidyl-tRNA, which is covalently linked to the growing polypeptide chain
  • Transiently binding to the outgoing deacylated tRNA
  • Editing the outgoing deacylated tRNA

Question 40

Question
During prokaryotic protein elongation, numerous ribosomal conformational changes occur. Which process involves GTP hydrolysis inducing a change in Elongation Factor-G, forcing movement of the ribosomal complex by one codon (relative to mRNA)?
Answer
  • Translocation
  • Formation of the peptide bond
  • Binding of specific aa - tRNA to A site
  • Exiting the ribosome

Question 41

Question
In prokaryotic protein elongation, which elongation factor is involved with the binding of specific aa-tRNA to the A site?
Answer
  • EF-Tu
  • EF-G
  • GTP
  • GDP

Question 42

Question
Prokaryotic protein termination requires the use of release factors since there are no tRNAs for the termination codons. If a release factor has bound near or at the A site - what can we assume about that RF? (select all that apply)
Answer
  • This release factor is structurally similar to tRNA.
  • It is bound with GTP and will use this GTP to hydrolyze the peptide bond in the P site.
  • It has recognized stop codon UAA, UAG, or UGA.
  • It is RF-3.

Question 43

Question
RRF, the ribosomal release factor, works together with EF-G and IF-1 to ___________ the two ribosomal subunits. This releases both tRNA and mRNA from the complex. IF-3 binds to IF-1 and the 30S subunit, blocking 50S re-association. Ultimately, this will _________ a new initiation complex.
Answer
  • dissociate, generate
  • bind, generate
  • activate, dissociate
  • dissociate, dissociate

Question 44

Question
Ribonucleic acid - protein complexes (RNP) form in eukaryotes and are essential for mRNA stability and regulation of translation. Which of the following is NOT an example of a structure bound within the closed loop mRNP complex?
Answer
  • Cap binding stabilization proteins CBP20, CBP80, and CBP220.
  • Cap binding translational initiation factors.
  • 3'polyA tail binding multiple polyA binding proteins.
  • 3'polyA tail binding translational initiation factors.

Question 45

Question
In eurkaryotes, translation is extremely efficient and a single activated mRNP complex can produce lots of protein from a single stabilized mRNA transcript. Essentially, this becomes a protein synthesis _____________.
Answer
  • Teeter-totter
  • Slide
  • Merry-go-round
  • Swing

Question 46

Question
There is an extremely toxic compound that disrupts ribosome function (elongation and translocation), blocking protein synthesis, leading to cell death. It consists of a B chain, which binds to the cells surface for cellular uptake, and an A chain, which depurinates and disrupts a highly conserved EF2 binding domain. Which of the following is NOT an enterotoxin that functions in a similar way?
Answer
  • Shiga
  • C. Diff
  • MRSA
  • E. Coli O157:H7

Question 47

Question
A 1-year-old male with chronic anemia is found to have B-thalassemia. Genetic analysis shows that one of his B-globin genes has a mutation that creates a new splice acceptor site 19 nucleotides upstream of the normal splice acceptor site of the first intron. Which of the following best describes the new mRNA molecule that can be produced from this mutant gene?
Answer
  • Exon 1 will be too short.
  • Exon 1 will be too long.
  • Exon 2 will be too short.
  • Exon 2 will be too long.

Question 48

Question
A 4-year-old child who becomes easily tired and has trouble walking is diagnosed with Duchenne muscular dystrophy, an X-linked recessive disorder. Genetic analysis shows that the patient's gene for the muscle protein dystrophin contains a mutation in its promoter region. Of the choices listed, which would be the most likely effect of this mutation?
Answer
  • Initiation of dystrophin transcription will be defective.
  • Termination of dystrophin transcription will be defective.
  • Capping of dystrophin mRNA will be defective.
  • Splicing of dystrophin mRNA will be defective.

Question 49

Question
A mutation to this sequence in eukaryotic mRNA will affect the process by which the 3'-end poly-A tail is added to the mRNA.
Answer
  • CAAT
  • CCA
  • GGGGCG
  • AAUAAA

Question 50

Question
A 20-year-old anemic man is found to have an abnormal form of B-globin that is 172 amino acids long, rather than the 141 found in the normal protein. Which of the following point mutations is consistent with that abnormality?
Answer
  • UAA -> CAA
  • UAA -> UAG
  • GAU -> GAC
  • GCA -> GAA

Question 51

Question
A pharmaceutical company is studying a new antibiotic that inhibits bacterial protein synthesis. When this antibiotic is added to an in vitro protein synthesis system that is translating the mRNA sequence AUGUUUUUUUAG, the only product formed is the dipeptide fMet-PHe. What step in protein synthesis is most likely inhibited by the antibiotic?
Answer
  • Initiation
  • Binding of charged tRNA to the ribosomal A site
  • Peptidyltransferase activity
  • Ribosomal translocation

Question 52

Question
Which of the following is required for both prokaryotic and eukaryotic protein synthesis?
Answer
  • Binding of the small ribosomal subunit to the Shine-Dalgarno sequence.
  • fMet-tRNA
  • Recognition of the 5'-cap by initiation factors.
  • Translocation of the peptidyl-tRNA from the A site to the P site.

Question 53

Question
Which of the following is best described as being trans-acting?
Answer
  • CAP site
  • Operator
  • Promoter
  • Repressor

Question 54

Question
The ZYA region of the lac operon will be efficiently transcribed if:
Answer
  • glucose and lactose are available.
  • cAMP levels are low.
  • the operator is mutated and can't be bound by the repressor.
  • the repressor is mutated and can't be bound by the inducer.
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