IMG test 3 version 3
mRNA is read in the _______ direction, which corresponds to the _______ of the protein being synthesized. a. 5' to 3'/N terminus to C terminus b. 3' to 5'/C terminus to N terminus c. 5't o 3'/C terminus to N terminus d. 3' to 5'/ 5' to 3' e. 3' to 5'/N terminus to C terminus
A
A mutant bacterial cell has a defective aminoacyl synthetase that attaches a lysine instead of phenylalanine to tRNAs with the AAA anticodon. 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 lysine-specifying 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.
B
One of the RNA polymerase I ancillary factors, SL1, consists of four proteins. One of its component proteins is also required for the initiation by RNA polymerase II and RNA polymerase III as a part of a "positioning" factor. This protein common to all three "positioning" factors is called _______. a. TFIID b. TBP c. TFIIIB d. UBF1 e. PABP
B
RNA polymerase and DNA polymerase differ in that a. All RNA polymerases use RNA as templates and all DNA polymerases use DNA templates. b. DNA polymerases synthesize DNA and RNA polymerases synthesize RNA c. RNA polymerase is much more accurate than DNA polymerase. d. DNA polymerase can initiate DNA synthesis, but RNA polymerase requires a primer to initiate RNA synthesis. e. All of the above.
B
Which of the following is (are) false about RNA? a. snoRNAs aid in processing pre-rRNA transcripts in the nucleolus. b. miRNAs are essential components of spliceosome. c. If it can form an appropriate 3D structure it may act as a catalyst, called ribozyme. d. snRNAs as parts of snurps are required for splicing of all nuclear pre-mRNAs e. none of the above.
B
Which of the following is true about the genetic code? a. It is read in groups of four nucleotides (bases) b. It is read in nonoverlapping triplets of nucleotides (bases) from a fixed point c. It is very different in prokaryotes and eukaryotes d. It is read in triplets of amino acids called codons e. It is read in overlapping triplets of nucleotides (bases) from a fixed point
B
Which of the following is/are true? a. RNAP III can initiate at its promoters in the absence of any additional factors b. RNAP III promoters usually contain positions that lie downstream of the startpoint c. RNAP III functions primarily within the nucleolus d. all of the above e. b. and c.only
B
A gene with 10 introns ________ exons a. has 9 d. has 12 b. has 10 e. may have a variable number of c. has 11
C
A scientist studying a "new" organism isolated RNA molecules that may have represented splicing intermediates, excised intron(s), and determined their structure. These molecules looked linear, no loops present, but they were branched and resembled the letter "y". From what you know about splicing/editing what is the most likely explanation of these results? a. group I introns were involved b. group II introns were involved c. trans splicing was taking place d. alternative tail signals were used e. this was RNA editing not splicing
C
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.
C
Alternative sigma factors are used as a means to regulate gene expression in bacteria. A replacement of one sigma factor for another on bacterial core RNA polymerase will enable __________ . a. a promoter to function as a terminator b. a terminator to function as promoter c. RNA polymerases to initiate transcription using a new (different) set of promoters d. RNA polymerase to read through transcription terminators e. RNA polymerase to terminate at a new set of terminators
C
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 the maximum number of different amino acids that could be accommodated by this genetic code assuming that at least two codons have to specify termination of translation (stop codons)? a. 5 b. 10 c. 23 d. 24 e. 25
C
Concerning the promoters recognized by general sigma factor in E. coli, mutations in the -10 region tend to affect the formation of the ______ complexes and the mutations in the -35 region affect the formation of the ______ complexes. a. closed/open d. open/open b. closed/closed e. closed or open depending on the gene c. open/closed
C
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. 5'-5' triphosphate bridge d. 3'-3' triphosphate bridge e. 5'-3' phosphodiester linkage
C
In the figure above the SR proteins bound to ESEs function as ____________. a. nucleases b. splicing repressors c. splicing activators d. snurps e. splicing catalysts
C
In the figure above the portion of the molecule labeled 5: a. is the 5' end of tRNA charged with an amino acid b. is the amino acid attached to the 3' end of the rRNA c. is a peptide or an amino acid d. is the last nucleotide at the 3' end of a tRNA e. All of the above
C
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.
C
Which of the following is false? a. RNA polymerase I (generally) requires only two ancillary factors for efficient initiation of transcription b. RNA polymerase I requires TBP for initiation of transcription c. RNA polymerase I transcribes 5S rRNA d. RNA polymerase I promoters are bipartite consisting of core promoter and UCE e. None of the above
C
Which of the following is not an activity of bacterial core RNA polymerase 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
C
Which of the following is/are true of snRNPs (snurps)? a. They bind to splice sites at each end of the exon. b. They are involved in splicing reactions of group II introns. c. They are made up of both protein(s) and RNA. d. all of the above. e. only a. and c
C
Which of the following statements best describes the termination of transcription by eukaryotic RNAP II? a. RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA. 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 the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase, which continues to synthesize more "nonfunctional" RNA. d. Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome. e. It may be a, b or c. depending on a gene.
C
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 polymerase(s) c. successive alternative ribosomes d. antitermination proteins e. b. and c.
C
Why must RNA splicing be absolutely precise? a. A single base error at a splice junction will cause a large deletion. b. A single base error at a splice junction will cause a large addition. c. A single base error at a splice junction will change the reading frame and result in mRNA mistranslation. d. A single base error at a splice junction will lead to premature transcription termination e. All of the above
C
Alternative splicing a. can allow the production of different mature mRNAs from a single gene. b. can allow the production of proteins of different sizes from a single gene. c. can allow the production of proteins with different amino acid sequences from a single gene. d. all of the above e. a. and b. only
D
Before RNA polymerase II can leave the promoter its CTD needs to be phosphorylated by the ____ activity of ___. a. phosphatase/TFIID b. kinase/TFIID c. phosphatase/TFIIH d. kinase/TFIIH e. ATPase/TFIIH
D
If antitermination is utilized to regulate gene expression, this mechanism enables _____ a. promoter to function as a terminator b. a terminator to function as promoter c. RNA polymerases to initiate transcription using a new (different) set of promoters d. RNA polymerase to read through transcription terminators e. RNA polymerase to terminate at a new set of promoters
D
If the triplet CCC codes for the amino acid proline in E. coli, then in tomato CCC should code for a. leucine. c. cysteine. e. impossible to predict. b. valine. d. proline.
D
Many of the RNA polymerase II promoters are TATA-less but they are still recognized by the same specific GTF in a sequence specific manner. These promoters must contain ______ plus DPE or DCE that are all recognized by a _______ subunit of ________. a. BRE element/TBP/TFIIB b. -35 hexamer/sigma/TFIID c. Inr/TBP/SL1 d. Inr/TAF/TFIID e. CAAT box/TBP/TFIID
D
Many of the RNAP II promoters contain ____, an element generally present at a "fixed" distance upstream from startpoint. When present, this element is bound by ____ via its subunit called ____. a. BRE element/TFIID/TAF b. -35hexamer/RNAP/sigma c. DPE element/TFIID/TAF d. TATA box/TFIID/TBP e. c. or d.
D
Muscle cells and nerve cells in humans owe their differences in structure and function to a. having different genes. b. having different chromosomes. c. using different genetic codes. d. differential gene expression. e. having unique ribosomes.
D
What is(are) the major difference(s) between intron removal in group I and group II introns? a. Group I introns are self-splicing but group II introns are not. b. Group I introns are not self-splicing but group II introns are. c. There are two transesterification reactions for group II introns but only one for group I introns. d. Group II introns are released as "lariats" but group I introns are released in a linear form. e. both c. and d.
D
What would most likely happen if SR proteins recruited U1 and U2AF (U2 will bind just upstream of U2AF) to the sites shown in the figure above and no other U1 or U2AF could bind anywhere else within this molecule? a. The spliceosome would not be able to assemble. b. The spliceosome would assemble but the RNA transcript would not be spliced. c. The RNA transcript would be spliced, joining exon 1 to exon 2. d. The RNA transcript would be spliced, joining exon 1 to exon 3. e. The RNA transcript would be spliced, joining exon 2 to exon 3
D
Which of the following are not transcribed from DNA? a. introns c. rRNA e. snoRNAs b. miRNAs d. poly A tails
D
Which of the following does not represent a function of TFIIH? a. It has a kinase activity necessary for CTD phosphorylation b. It is required for promoter clearance by RNA Pol. II. c. It is involved in TCR when RNA Pol. II stalls at a lesion. d. It has a phosphatase activity necessary for transcript modification. e. It has a helicase activity necessary for the formation of an open complex.
D
Which of the following is characteristic of the lytic cycle? a. Many bacterial cells containing viral DNA are produced. b. Viral DNA is incorporated into the host genome. c. The viral genome replicates without destroying the host. d. New phages are produced and released while killing the host. e. The virus-host relationship usually lasts for generations.
D
Which of the following is false about miRNAs? a. most of them are transcribed by RNA Pol II. b. they may modulate gene expression by inhibiting or stimulating translation of specific "complementary" mRNAs c. they may modulate gene expression by having an effect on transcript stability. d. none of the above e. a. and c. only
D
Which of the following is false about nuclear genes for the 3 largest rRNAs in higher eukaryotes? a. they are transcribed in the nucleolus b. each "gene" is transcribed into a large precursor RNA that needs to be cut and trimmed to give rise to 3 mature rRNAs c. they are transcribed by RNA Pol I d. they are translated into r-proteins in the cytoplasm e. none of the above is false; all are true
D
Which of the following is false about reverse transcriptase? a. It is a type of DNA polymerase. b. It requires a primer. c. It can add nucleotides only to the 3' end of the growing chain. d. It is a type of RNA polymerase e. None because all of the above are true
D
Which of the following may affect the stability of an eukaryotic mRNA? a. miRNA b. 5' G-cap c. poly A tail d. all of the above e. a. and b. only
D
Which of the following statements best describes the termination of transcription in prokaryotes? a. RNA polymerase transcribes through a stop codon, causing the polymerase to stop advancing through the gene and release the mRNA. b. Once transcription has initiated, RNA polymerase transcribes until it reaches the end of the chromosome. c. RNA polymerase transcribes through an intron, and the snRNPs cause the polymerase to let go of the transcript. d. RNA polymerase transcribes through the terminator sequence, causing the polymerase to release the transcript and dissociate from DNA. e. RNA polymerase transcribes through the polyadenylation signal, causing proteins to associate with the transcript and cut it free from the polymerase.
D
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
D
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. An alternative, further downstream tail signal was utilized in generation of head transcripts. d. mRNAs in the thorax are edited by ADAR resulting in a premature stop codon e. mRNAs in the head region are edited by CDAR generating a premature stop codon.
E
A specific eukaryotic transcription unit that is 10,000 nucleotides long uses only 1,200 nucleotides to make a protein consisting of 400 amino acids. This is best explained by the fact that a. it may contain several introns that are spliced out. b. there is redundancy and ambiguity in the genetic code. c. many nucleotides may be present within 5' and 3'UTRs. d. nucleotides break off and are lost during the transcription process. e. a. and c. only
E
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
E
In the figure above the ESEs are __________ a. trans acting factors b. cis-acting elements c. splicing activators d. sites within RNA e. both b. and d.
E
Many eukaryotic DNA sequences may code for more than one protein in the following way(s) except: a. different pre-mRNAs with different alternative exons may be generated by using two different polyadenylation sites. b. different pre-mRNAs with different alternative exons may be generated by using two different promoters. c. alternative splicing of the same pre-mRNA can generate mature transcripts with different combinations of exons. d. different proteins may be generated by mRNA editing that could convert a codon for one amino acid into a codon for another amino acid or into a stop codon. e. none of the above because each one of these could be used.
E
Refer to figure above. Which of the following codons (all written in 5' to 3') would be recognized by this tRNA? a. CUU b. UUU c. TTC d. UUC e. b. or d.
E
There are 61 mRNA sense codons, that specify 20 amino acids, but only 45 tRNAs (even fewer in some organisms). 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 more flexible than in the 1st and 2nd positions. c. many codons are never used, so the tRNAs that recognize them are dispensable. d. all of the above e. a. and b. only
E
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. nontemplate/noncoding e. both b. and d. are correct
E
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 RNA molecules can be transcribed from a single gene, increasing the potential rate of gene expression. d. all of the above e. b. and c. only
E
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
E
Which of the following is a type of cis-acting element primarily "acting" in RNA rather than DNA? a. (ISS) intronic splicing silencer b. operator c. intrinsic transcription terminator d. all of the above e. a. and c. only
E
Which of the following most accurately describes Met-tRNAAla? a. A tRNA with an anticodon for Ala charged with Met b. A tRNA for Met charged with Alanine c. An uncharged tRNA for Met d. A tRNA for Ala charged with Met e. both a. and d.
E