Molecular Genetics Exam III
An extraterrestrial life form is discovered. It has a genetic code much like that of organisms on Earth except that there are five different DNA bases instead of four and the base sequences are translated as doublets instead of triplets. What is a maximum number of different amino acids that could be accommodated by this genetic code assuming that at least one codon is nonsense (stop)? a. 5 b. 9 c. 10 d. 24 e. 25
24
RNA polymerase moves along the template strand of DNA in the ____ direction, and adds nucleotides to the ____ end of the growing transcript. a. 3' to 5'; 5' b. 3' to 5'; 3' c. 5' to 3'; 5' d. 5' to 3'; 3' e. b or d depending on the gene
3' to 5'; 3'
Bacterial RNA polymerase passes through several steps prior to elongation. These steps include 1. release or change of association with sigma, 2. formation of an open binary complex, 3. formation of a closed binary complex, 4. abortive initiation. The correct sequence of events is: a. 3-1-2-4 b. 2-3-4-1 c. 3-2-4-1 d. 3-2-1-4 e. 2-4-1-3
3-2-4-1
Choose the answer that has these events of protein synthesis in the proper sequence. 1. An aminoacyl-tRNA binds to the A site. 2. A peptide bond forms between the new amino acid and a polypeptide chain. 3. Release factor interacts with codon located within A site. 4. A small ribosomal subunit binds with mRNA. 5. tRNA translocates to the P site. a. 1, 3, 2, 4, 5 b. 4, 1, 2, 5, 3 c. 5, 4, 3, 2, 1 d. 4, 1, 3, 2, 5 e. 2, 4, 5, 1, 3
4, 1, 2, 5, 3
How would one describe the bond that holds the inverted methylguanosine cap on the 5' end of a mature eukaryotic mRNA? a. 5'-3' triphosphate bridge b. 3'-5' triphosphate bridge c. 3'-3' triphosphate bridge d. 5'-5' triphosphate bridge e. 5'-3' phosphodiester linkage
5'-5' triphosphate bridge
There are 61 mRNA codons that specify an amino acid, but only (about) 45 tRNAs. This is best explained by the fact that a. some tRNAs have anticodons that recognize two or more different codons. b. the rules for base pairing between the third base of a codon and tRNA are flexible. c. many codons are never used, so the tRNAs that recognize them are dispensable. d. A and B only e. A, B, and C
A and B only
Which of the following most accurately describes Met-tRNA i? a. An uncharged eukaryotic initiator tRNA b. A charged eukaryotic initiator tRNA c. A charged tRNA for Met used in eukaryotes for either elongation or initiation d. A charged tRNA for Met that can be used in elongation only e. A charged prokaryotic initiator tRNA
A charged eukaryotic initiator tRNA
The optimal promoter for the RNA polymerase holoenzyme with the general sigma factor in E. coli consists of the following features: a. A purine startpoint, -10 hexamer composed mostly of Gs and Cs and -35 hexamer separated from -10 region by at least 20 nucleotides b. A pyrimidine startpoint, -10 hexamer composed mostly of As and Cs and -35 hexamer separated from -10 region by 17 nucleotides c. A purine startpoint, -10 hexamer composed only of As and Ts and -35 hexamer separated from -10 region by 17 nucleotides d. A purine startpoint, -10 pentamer composed only of As and Ts and -35 pentamer separated from -10 region by more than 20 nucleotides e. Both b. and c. would work equally well
A purine startpoint, -10 hexamer composed only of As and Ts and -35 hexamer separated from -10 region by 17 nucleotides
During translation, chain elongation continues until what happens? a. No further amino acids are needed by the cell. b. All tRNAs are empty. c. The polypeptide is long enough. d. A stop codon is encountered. e. The ribosomes run off the end of mRNA.
A stop codon is encountered.
Which of the following most accurately describes Ala-tRNA Cys? a. A tRNA for Ala (alanine) charged with Cys (cysteine) b. A tRNA for Ala mutated to recognize a Cys codon c. A tRNA for Cys charged with Ala d. A tRNA for Cys mutated to recognize an Ala codon e. An initiator tRNA
A tRNA for Cys charged with Ala
The function of the ribosome in polypeptide synthesis is to a. hold mRNA and tRNAs together. b. catalyze the addition of amino acids from tRNAs to the growing polypeptide chain. c. move along the mRNA and eject tRNAs during the translocation process. d. A and B only e. A, B, and C
A, B, and C
Transposable elements a. are discrete sequences in a genome that "are" mobile b. when mobilized may produce mutations c. called retroposons require an RNA intermediate for transposition d. All of the above e. None of the above
All of the above
Which of the following is true about the E. coli sigma factors a. they contact promoters directly in a sequence specific manner b. they determine which genes are going to be transcribed by the core polymerase c. lone sigma do not bind promoters d. a. and c. only e. All of the above
All of the above
Which of the following statements is true about transcription termination in E.coli. a. The responsibility for termination lies (primarily) in the sequences already transcribed b. Intrinsic terminators do not require additional factors, core enzyme is sufficient for termination to occur (at least in vitro). c. E.coli transcription terminators are cis -acting elements d. Rho-dependent terminators require rho factor in addition to RNA polymerase e. All of the above
All of the above
Which of the following is/are false about prokaryotic ribosomes a. They have 3 tRNA-binding sites: E, P and A b. An aminoacyl-tRNA enters the A site c. peptidyl-tRNA (after each translocation) is bound in the P site d. An aminoacyl-tRNA exits via E site e. none of the above; they are all true
An aminoacyl-tRNA exits via E site
What is a ribozyme? a. An enzyme that uses RNA as a substrate b. An enzyme made up of RNA c. An enzyme that catalyzes the association between the two ribosomal subunits d. An enzyme that synthesizes RNA as part of the transcription process e. An enzyme that synthesizes RNA primers during DNA replication
An enzyme made up of RNA
Using RNA as a template for protein synthesis instead of translating proteins directly from the DNA is advantageous for the cell because a. RNA is much more stable than DNA. b. RNA acts as an expendable copy of the genetic material, allowing the DNA to serve as a permanent, pristine repository of the genetic material. c. many mRNA molecules can be transcribed from a single gene, increasing the potential rate of gene expression. d. B and C only e. A, B, and C
B and C only
The internal mechanisms that has evolved in many organisms to help them deal with a cyclic 24- hour world is called? a. Biological Clock b. Oscillator c. Perpetual Clock d. Circadian Clock e. Rhythmic clock
Circadian Clock
What does COI stand for? a. Coenzyme 1 b. Coupled operator 1 c. Cytochrome Oxide Isomerase d. Cytochrome Oxidase 1 e. a. or d.
Cytochrome Oxidase 1
The genetic code is essentially the same for all organisms. From this, one can logically assume all of the following except a. a gene from an organism could theoretically be expressed by any other organism. b. all organisms have a common ancestor. c. DNA was the first genetic material. d. the same codons in different organisms usually translate into the same amino acids. e. different organisms have the same number of different types of amino acids.
DNA was the first genetic material
All of the following are directly involved in translation except a. mRNA b. tRNA c. ribosomes d. DNA e. aminoacyl-tRNA synthetase enzymes
DNA.
Before RNA polymerase II can leave the promoter its CTD needs to be phosphorylated by the __________ activity of TFIIH a. phosphatase b. kinase c. helicase d. peptidyl transferase e. isomerase
kinase
Which of the following is most likely to interact with a Met-tRNA? a. EF-Ts b. EF-Tu-GTP c. IF-1 d. EF-Tu-GDP e. a partial P site on the (free) small ribosomal subunit
EF-Tu-GTP
Which of the following is most likely to interact with a charged initiator tRNA? a. a full A site on the ribosome b. a full P site on the ribosome c. a partial A site on the large ribosomal subunit d. IF-2 or eIF-2 e. All of the above
IF-2 or eIF-2
A DNA sequence (an element) that can negatively regulate gene expression from a distance by being positioned between the promoter and enhancer is called _________ a. silencer b. operator c. upstream control element d. Insulator e. Terminator
Insulator
Which of the following is/are false about IRES? a. It stands for Internal Ribosome Entry Site b. It is frequently used in bacterial translation initiation when RBS is absent c. It allows cap-independent translation initiation in eukaryotic cells d. It may be used as a target for drugs against some human viral infections e. none of the above
It is frequently used in bacterial translation initiation when RBS is absent
Which of the following is/are false about mortalin? a. It is encoded by a nuclear gene. b. It is a type of heat shock chaperone primarily fond in mitochondrial matrix. c. Some variants in its coding region may increase susceptibility to Parkinson's disease. d. It is involved in exporting some mitochondrial proteins to cytoplasm. e. It may be involved in cellular aging.
It is involved in exporting some mitochondrial proteins to cytoplasm.
The production of a new s factor that can recognize a different promoter can have what effect on an organism? a. It can shorten proteins synthesized from the corresponding promoter. b. It can lead to the coordinated destruction of already existing proteins. c. It can lead to coordinated denaturation of the cell's DNA. d. It leads to the coordinated transcription of a battery of genes that respond to a particular environmental stimulus. e. It leads to the coordinated denaturation of a battery of specific gene products.
It leads to the coordinated transcription of a battery of genes that respond to a particular environmental stimulus
Statement A. Eukaryotic RNA Pol. I transcribes both the rRNA and tRNA genes Statement B. Eukaryotic RNA Pol. III transcribes large rRNAs a. Only A. is true c. Both A. and B. is true b. Only B. is true d. Neither A. nor B. is true
Neither A. nor B. is true
Statement A. In prokaryotes there is a single RNA Polymerase that transcribes all the genes in that organism Statement B. In prokaryotes the identity of the sigma factor present in the holoenzyme determines which promoter(s) are bound by the RNA Pol. and which set of genes can be transcribed. a. Only A. is true b. only B. is true c. Both A. and B. are true d. Neither A. nor B. is true
Only A. is true
What does ORF stand for? a. Oxidizing Reagent F b. Oxygen Reducing Factor c. Operator Recognition Factor d. Open Reading Frame e. Ordered Restriction Fragments
Open Reading Frame
The enzyme peptidyl transferase, which catalyzes the transfer of the polypeptide chain attached to the tRNA in the _______ site to the aminoacyl-tRNA in the _______ site, is a(an) ____________. a. A; P; ribosomal protein b. P; A; rRNA of the small ribosomal subunit c. A; P; rRNA of the small ribosomal subunit d. P; A; rRNA of the large ribosomal subunit e. P; A; ribosomal protein
P; A; rRNA of the large ribosomal subunit
The enzyme peptidyl transferase, which catalyzes the transfer of the polypeptide chain attached to the tRNA in the _____site to the aminoacyl-tRNA in the ____site, is a (an) _____. a. A; P; r-protein of the small ribosomal subunit. b. P; A; rRNA of the small ribosomal subunit. c. A; P; rRNA of the small ribosomal subunit d. P; A; rRNA of the large ribosomal subunit e. P; A; r-protein of the large ribosomal subunit
P; A; rRNA of the large ribosomal subunit
All mRNAs contain all of the following except: a. 3' - UTR b. coding sequence c. Poly A tail d. 5'-UTR e. c. and d.
Poly A tail
Which of the following is the "positioning' factor for RNA polymerase II and the first one of the general factors that needs to bind the promoter before other factors can join in. a. TFIIA c. TFIIIB e. TFIIE b. TFIIB d. TFIID
TFIID
_____________ and all the general factors (TFII'X"s) comprise a basal transcription apparatus. a. Sigma factor b. RNA polymerase I c. RNA polymerase II d. A core promoter e. Chromatin
RNA polymerase II
RNA polymerase and DNA polymerase differ in that a. RNA polymerase uses RNA as a template, and DNA polymerase uses a DNA template. b. RNA polymerase binds to single-stranded DNA, and DNA polymerase binds to doublestranded DNA. c. RNA polymerase is much more accurate than DNA polymerase. d. RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis. e. RNA polymerase does not need to separate the two strands of DNA in order to synthesize an RNA copy, whereas DNA polymerase must unwind the double helix before it can replicate the DNA.
RNA polymerase can initiate RNA synthesis, but DNA polymerase requires a primer to initiate DNA synthesis
Which of the following statements best describes the termination of transcription in prokaryotes? a. RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase. b. RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript. c. RNA polymerase transcribes through an intron, and the snRNPs cause the polymerase to let go of the transcript. d. Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome. e. RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA.
RNA polymerase transcribes through the terminator sequence, causing the polymerase to fall off the DNA and release the transcript
What does SNP stand for? a. Small Nuclear Protein b. Small Nucleoprotein Particle c. Simple Nucleotide Particle d. Single Nucleotide Polymorphism e. Simple Nuclear Pore
Single Nucleotide Polymorphism
DNA is composed of two strands, only one of which typically is used as a template for RNA synthesis. By what mechanism is the correct strand chosen? a. Both strands are tried and the one that works is remembered. b. Only one strand has the start codon. c. The promoter acts to aim (position) the RNA polymerase. d. A start factor informs the system. e. It is chosen randomly.
The promoter acts to aim (position) the RNA polymerase
Which of the following statements is false? a. The "simplest" types of transposable elements are bacterial insertion sequences (IS) b. Composite transposons have terminal modules that consist of IS elements c. The IS module(s) of a composite transposon provide(s) transposase activity d. The region between two IS modules of a composite transposon provides transposase activity e. None of the above is false, they are all true
The region between two IS modules of a composite transposon provides transposase activity
Which of the following is False about a transcription unit a. It is a region of DNA expressed via the production of a single RNA molecule b. The startpoint is assigned a value of 0 (on DNA) c. It always includes nucleotides (bases) assigned only positive values d. It may consist of several genes e. None of the above
The startpoint is assigned a value of 0 (on DNA)
Which of the following is/are false about miRNAs? a. They are encoded by nuclear genomes b. They are non-coding regulatory "small" RNAs c. They may affect gene expression by blocking translation or decreasing transcript stability d. They are derived from dsRNA of viral origin e. none of the above
They are derived from dsRNA of viral origin
Which of the following is neither an initiator nor a terminator codon? a. UAG b. UGA c. UGG d. UAA e. AUG
UGG
A G-cap a. may protect newly synthesized mRNA from degradation.. b. is required for translation of eukaryotic mRNAs c. is added to some eukaryotic mRNAs after transcription. d. a and b only e. a, b and c
a and b only
Gene silencing without changing DNA sequence _____________ a. is called an epigenetic effect. b. may be accomplished by DNA methylation. c. is accomplished by histone acetylation. d. all of the above e. a. and b. only
a and b only
Each spliceosome consists of a variety of proteins and a number of distinct ribonucleoprotein particles. These ribonucleoprotein particles are referred to by a briefer name. What is it? a. snRNPs c. "snurps" b. snRUPs d. ribosomes e. a and c
a and c
Which of the following events can occur co-transcriptionally in eukaryotes? a. capping b. translation c. splicing d. all of the above e. a. and c. only
a and c only
Which of the following is/are not the function of Class I Release Factor (RF1 for example)? a. recognition of termination codons. b. participation in peptidyl-tRNA linkage hydrolysis c. interaction with Class II RFs d. interaction with the A site of ribosome e. interaction with the P site of ribosome
interaction with the P site of ribosome
In the process of bacterial protein synthesis ribosomal RNAs (rRNAs) _______. a. catalyze peptide bond formation b. interact (by base pairing) with mRNA during initiation c. provide many of the contacts between the subunits in the 70S ribosome d. interact with tRNAs in both the A and P sites e. all of the above
all of the above
Which of the following is true about retroviruses? a. Their genomes encode integrase that is analogous to transposase b. As proviruses they are flanked by short direct repeats of the host target DNA c. Their normal life cycle includes provirus stage d. The DNA of a provirus and its corresponding RNA genome have different terminal sequences e. all of the above are true
all of the above are true
Retroviruses a. have genomes of double stranded RNA b. are RNA viruses that use a provirus stage as a normal part of their "life" cycle c. are common in prokaryotes d. immediately upon infection insert their DNA genomes into the host genome e. all of the above are true about retroviruses
are RNA viruses that use a provirus stage as a normal part of their "life" cycle
Ty elements a. are transposons in yeast (similar to bacterial transposons) that transpose via replicative mechanism requiring transposase and resolvase functions b. are the most common transposons in prokaryotes c. are yeast retroposons utilizing RNA intermediate in the process of transposition d. are all processed pseudogenes that cannot be expressed e. are yeast retroviruses that are capable of infecting neighboring cells
are yeast retroposons utilizing RNA intermediate in the process of transposition
During protein synthesis, ribosomes: a. attach to the mRNA molecule and 'travel" along its length. b. attach to the DNA molecule and "travel" along its length to produce an mRNA molecule. c. translate mRNA into tRNA. d. transcribe mRNA to tRNA. e. translate mRNA into DNA.
attach to the mRNA molecule and 'travel" along its length.
The RBS or S-D sequence is a consensus sequence found upstream of the start site in mRNAs transcribed from what type of genes? a. eukaryotic b. phage c. bacterial d. all of the above e. b. and c. only
b and c only
Replicative transposition a. generally results in a chromosomal break at the donor site b. increases the number of transposable elements in the genome c. generally does not change the donor site d. usually does not involve transposase activity e. b. and c. are both true
b. and c. are both true
Statement A: All prokaryotic mRNAs have a Shine-Dalgarno sequence that is necessary for binding to the small ribosomal subunit via base pairing with a complementary sequence present in rRNA Statement B: Eukaryotic mRNAs do not have Shine-Dalgarno sequences but instead, in order to be translated, they must have either 5'G cap or an IRES. a. only A is true b. only B is true c. both A and B are true d. neither A nor B is true
both A and B are true
Statement A: The active binary complex (elongation factor EF-Tu+ GTP) is required to bring the charged tRNA to the A site of the ribosome Statement B: EF-Ts is required for regeneration of active binary complex (EF-Tu+GDP to EF- Tu+GTP) a. only A is true b. only B is true c. both A and B are true d. neither A nor B is true
both A and B are true
Statement A: Human genome may contain about 850,000 copies of LINES (long interspersed sequences) that all correspond to non-protein coding processed pseudogenes that originated as products of RNA pol III Statement B: Human genome contains about 1,500,000 copies of SINES (short interspersed sequences) which encode reverse transcriptase and integrase with very close similarities to retroviral proteins a. only A. is true b. only B. is true c. both A. and B. are true d. both A. and B. are false
both A. and B. are false
Statement A. Intrinsic transcription terminators consist of two features that are both required for termination to occur: a hairpin that is followed by a run of Us Statement B. Antitermination is a mechanism that allows RNA polymerase to continue transcription past terminators a. only A. is true b. only B. is true c. both A. and B. are true d. neither A. nor B. is true, both are false
both A. and B. are true
Statement A. Transposition generally does not rely on any relationship between the sequences at the donor and recipient (target) sites. Statement B. The stagger between the cuts on two strands of target DNA determines the length of the direct repeats flanking transposons a. only A. is true b. only B. is true c. both A. and B. are true d. both A. and B. are false
both A. and B. are true
Statement A. lac operon is regulated by both positive and negative control mechanisms Statement B. trp operon in E. coli is regulated by both repression and attenuation a. only A. is true b. only B. is true c. both A. and B. are true d. neither A. nor B. is true, both are false
both A. and B. are true
Which of the following helps to stabilize mRNA by inhibiting its degradation? a. TATA box b. DPE c. 5' cap d. poly-A tail e. both C and D
both C and D
Numts are all of the following except: a. nuclear sequences transferred to mitochondrial genomes b. mitochondrial DNA sequences transferred to nuclear genomes c. usually representing non-functional pseudogenes d. useful for phylogenetic analysis e. both a. and d.
both a and d
Which of the following is inconsistent with the Central Dogma? a. information in nucleic acids can be perpetuated b. information in proteins can be perpetuated c. transfer of information into RNA is irreversible d. transfer of information into protein is irreversible e. both B and C
both b and c
Accuracy in the translation of mRNA into the primary structure of a protein depends on specificity in the a. binding of ribosomes to mRNA. b. shape of the A and P sites of ribosomes. c. bonding of the anticodon to the codon. d. attachment of amino acids to tRNAs. e. both c. and d.
both c and d
What are ribosomes composed of? a. rRNA only b. proteins only c. both rRNA and protein d. mRNA, rRNA, and protein e. mRNA, tRNA, rRNA, and protein
both rRNA and protein
Concerning the promoters recognized by general sigma factor ( s70) in E. coli, mutations in the -35 region tend to affect the formation of the ______ and the mutations in the -10 region affect the formation of the _______ binary complexes. a. closed/open b. closed/closed c. open/closed d. open/open e. any of the above because it varies greatly from promoter to promoter
closed/open
DNA footprinting is a technique for studying __________ a. direct protein-protein interactions b. direct protein-DNA interactions c. DNA-DNA base pairing d. RNA-DNA base pairing e. all of the above
direct protein-DNA interactions
When does translation begin in prokaryotic cells? a. only after the completed mRNA is released from RNAP b. during transcription c. after the 5' cap is added to mRNA d. once the pre-mRNA has been converted to mRNA e. as soon as the DNA introns are removed from the template
during transcription
A DNA sequence containing regulatory elements (binding sites for transcription factors) that can influence transcription activation from a distant location that may even be downstream from the regulated gene is called ______ . a. promoter b. operator c. upstream control element d. enhancer e. terminator
enhancer
If you isolated mutant bacteria that express lac operon constitutively (in the absence of glucose and lactose) the most likely explanation is that a. the operator is mutated so that the repressor cannot bind to it b. the repressor is absent c. the repressor is mutated so it can't bind to the operator d. everyone of the above is possible but can't tell which one is the real reason without additional information e. none of the above
everyone of the above is possible but can't tell which one is the real reason without additional information
Nonreplicative transposition a. generally results in a chromosomal break at the donor site b. generally increases the number of transposable elements in the genome c. generally does not change the donor site d. usually does not involve transposase activity e. none of the above
generally results in a chromosomal break at the donor site
Which of the following is true for both prokaryotic and eukaryotic gene expression? a. After transcription, a 3' poly-A tail and a 5' cap are added to mRNA. b. Translation of mRNA can begin before transcription is complete. c. RNA polymerase assisted by a sigma factor binds to the promoter region to begin transcription. d. mRNA is synthesized in the 5' to 3' direction. e. The mRNA transcript is the exact complement of the gene from which it was copied.
mRNA is synthesized in the 5' to 3' direction
A scientist studying fly development isolates two proteins encoded by the same gene that differ from each other by the length of the C-terminal domain. The protein isolated from the head region is identical to the one from the thorax in the N-terminal region but is shorter by 30 amino acids. Analysis of gene sequence indicates a presence of a single ORF that would lead to the production of the longer peptide, the one produced in the thorax . What is the most likely mechanism responsible for the production of the two different peptides encoded by this gene? a. The gene is transcribed from different promoters in different body regions resulting in different transcripts and then different peptides. b. Pre-mRNAs in the two body regions are alternatively spliced resulting in different mature mRNAs encoding different peptides. c. mRNAs in the head region are edited by CDAR generating a premature stop codon. d. mRNAs in the thorax are edited by ADAR resulting in a premature stop codon e. An alternative, further downstream tail signal was utilized in generation of head transcripts.
mRNAs in the head region are edited by CDAR generating a premature stop codon
Following peptide bond formation between the amino acid in the A site on the ribosome and the growing polypeptide chain, the tRNA in the A site: a. releases the growing polypeptide chain. b. picks up another amino acid to add to the chain. c. moves to the P site of the ribosome. d. forms a peptide bond with A site of the ribosome. e. forms a covalent bond with the P site of the ribosome.
moves to the P site of the ribosome.
Some DNA sequences may code for more than one protein in the following way(s) except: a. two proteins can be generated from a single gene by using different start codons in the mRNA. b. two genes may share the same sequence by reading the DNA in different frames. c. alternative splicing of the same pre-mRNA can generate mature transcripts with different combinations of exons. d. two proteins may be generated by RNA editing that changes a stop codon into an amino acid codon (or vice versa) generating proteins of different lenghts. e. none of the above.
none of the above
Which of the following is/are false? a. IF-1 prevents aa-tRNAs from entering the partial A site on 30S b. IF-2-GTP "places" fMet-tRNA in the partial P site of 30S c. IF-3 when bound to 30S prevents binding of 50S to it d. none of the above e. all of the above
none of the above
One of the termination codons is 5'-UGA-3'. Its corresponding anticodon in normal tRNA is: a. 3'-ACT-5'. b. 3'-ACU-5'. c. 3'-UCA-5'. d. 5'-TCA-3'. e. none of the above because there are no "normal" tRNAs that recognize termination codons
none of the above because there are no "normal" tRNAs that recognize termination codons
Histone acetylases and deacetylases (like HDA6) may have an effect on gene expression when they are localized to ____________. a. Mitochondria b. endoplasmic reticulum c. nucleus d. cytoplasm e. plasma membrane
nucleus
Termination (termination and ribosome recycling) of translation involves all of the following except a. a reaction of peptidyl-tRNA with water (hydrolysis) b. participation of RFs c. dissociation of ribosome from mRNA d. peptide bond formation e. expulsion of the last tRNA from ribosome
peptide bond formation
The 3' end of most eukaryotic mRNAs contains a ______, while the 5' end has a____ a. poly(A) tail, methylated guanosine cap b. poly(U) tail, methylated guanosine cap c. methylated guanosine cap, poly(A) tail d. poly(A) tail, sulfonated guanosine cap e. methylated guanosine cap, poly(U) tail
poly(A) tail, methylated guanosine cap
Which of the following processes is the least likely control point for gene expression in prokaryotes? a. initiation of transcription b. termination of transcription c. processing of transcript d. translation of mRNA e. posttranslational modification
processing of transcript
If the triplet CCC codes for the amino acid proline in E. coli, then in tomato CCC should code for a. leucine. b. valine. c. cysteine. d. proline. e. impossible to predict
proline
Bacteriophage DNA that have become integrated into the host cell chromosome are called a. intemperate bacteriophages. b. transposons c. prophages d. T-even phages e. plasmids
prophages
A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine to tRNAs with the anticodon AAA instead of a phenylalanine. The consequence of this for the cell will be that a. none of the proteins in the cell will contain phenylalanine. b. proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU. c. the cell will compensate for the defect by attaching phenylalanine to tRNAs with lysinespecifying anticodons. d. the ribosome will skip a codon every time a UUU is encountered. e. None of the above will occur; the cell will recognize the error and destroy the tRNA.
proteins in the cell will include lysine instead of phenylalanine at amino acid positions specified by the codon UUU
Which of the following is NOT an activity of bacterial RNA polymerase core enzyme or any of the eukaryotic RNAPs (I, II, and III)? a. unwinding and rewinding of DNA b. catalyzing addition of ribonucleotides c. recognition of promoters d. holding a newly synthesized portion of RNA product e. holding separated DNA strands
recognition of promoters
Transcription involves synthesis of an RNA chain representing one strand of a DNA duplex. The strand that has the "same" sequence as the RNA product is the ________ strand and the one with complementary sequence (to RNA) is the ________ strand a. antisense/sense b. sense/antisense c. template/coding d. template/antisense e. both b. and d. are correct
sense/antisense
The intermediate stage/form that the pre-mRNA introns pass through while undergoing splicing by __________ is called the ___________. a. spliceosome/langolier b. snRNP/lanyard c. spileosome/lariat d. ribosome/lasso e. snRNA/ elsesser
spileosome/lariat
During splicing of nuclear pre-mRNAs the splicing apparatus called _______has to be assembled in a specific sequence in order to precisely remove all of the _______ and splice together the ____. a. spliceosome/exons/introns b. ribosome/introns/exons c. RNAP holoenzyme/exons/introns d. CTD tail/introns/exons e. spliceosome/introns/exons
spliceosome/introns/exons
Varied association times of different snurps with mRNA support which of the following? a. holospliceosome model b. step-wise model of spliceosome assembly c. the conclusion that splicing takes ~30 sec. d. all of the above e. b. and c. only
step-wise model of spliceosome assembly
Which of the following strategies is NOT used by phages to organize the expression of their genes into regulatory cascades a. successive alternative sigma factors b. phage specific RNA polymerases c. antitermination proteins d. successive alternative ribosomes e. All of the above may be used by different phages
successive alternative ribosomes
Organisms produce different proteins at different developmental stages, under different environmental conditions, in different cell types (in multicellular organisms) etc. Gene expression can be regulated at several different levels. Which of the following is the least likely control point for gene expression in eukaryotes? a. initiation of transcription b. activation of gene "structure" c. termination of transcription d. processing of transcript e. translation of mRNA
termination of transcription
In some cases a nonsense mutation in one gene of a bacterial polycistronic transcription unit prevents the expression of the downstream (or subsequent) genes in the same unit, an effect referred to as polarity. The most likely explanation for this phenomenon is that a. the downstream genes are transcribed but not translated because nonsense mutations result in translation termination b. the promoter is not recognized and the transcription is not initiated c. the downstream genes are not recognized by DNA polymerase and thus not replicated d. the downstream genes are not transcribed because of premature transcription termination caused by the exposure of cryptic intrinsic terminators e. the downstream genes are not transcribed because of premature transcription termination caused by the exposure of cryptic rho-dependent terminators
the downstream genes are not transcribed because of premature transcription termination caused by the exposure of cryptic rho-dependent terminators
Which of the following is FALSE about bacterial RNA polymerase catalyzed reactions (synthesis of RNA) a. NTPs act as substrates b. new nucleotides are always added at the 3' end c. these reactions occur at the catalytic site located in the sigma subunit d. they can occur in the absence of sigma e. none of the above
these reactions occur at the catalytic site located in the sigma subunit
Wobble hypothesis accounts for the ability of some tRNAs _______ a. to be recognized by more than one aminoacyl-tRNA synthetase b. to recognize more than one anticodon c. to recognize more than one codon by unusual pairing with first base of the codon d. to recognize more than one codon by unusual pairing with third base of the codon e. to have modified bases in the anticodon loop
to recognize more than one codon by unusual pairing with third base of the codon
In the regulation of trp operon, the repressor which is _______ binds to the operator which is __________. This operon is also controlled by attenuation and the "attenuator" is _________. a. cis-acting / trans-acting trans-acting b. cis-acting / cis-acting / trans-acting c. trans-acting / cis-acting/ cis-acting d. trans-acting / cis-acting / trans-acting e. cis-acting / cis-acting/ cis-acting
trans-acting / cis-acting/ cis-acting
What type of mechanism could result in joining of RNA fragments originating from two different transcription units. a. RNA editing b. self splicing c. cis-splicing d. trans-splicing e. none of the above
trans-splicing
A geneticist introduces a transgene into yeast cells and isolates five independent cell lines in which the transgene has integrated into the yeast genome. In four of the lines, the transgene is expressed strongly, but in the fifth there is no expression at all. A likely explanation for the lack of transgene expression in the fifth cell line is that the a. transgene integrated into a heterochromatic region of the genome. b. transgene integrated into a euchromatic region of the genome. c. transgene was mutated during the process of integration into the host cell genome. d. host cell lacks the enzymes necessary to express the transgene. e. transgene integrated into a region of the genome characterized by high histone acetylation.
transgene integrated into a heterochromatic region of the genome
Which of the following processes is the least likely control point for gene expression in prokaryotes? a. transport of transcript out of nucleus b. initiation of transcription c. termination of transcription d. translation of mRNA e. can't be determined without additional information
transport of transcript out of nucleus
