Exam 3 Flashcards
n E. coli, a protein that has a helix-turn-helix motif is likely to
A. prevent adenylate cyclase from functioning
B. bind to B-galactosidase to regulate its functioning
C. bind to a repressor protein and cause it to fall off a stretch of DNA
D. bind to a stretch of DNA
E. cause catabolite repression of gene expression
D
In eukaryotes, TATA sites can typically be found in
A. exons B. introns C. promoter sequences D. proximal promotor element sites E. enhancer regions
C
Which of the following statements best defines the term operon?
A. An operon is a region of DNA that consists of a single gene regulated by more than one promoter.
B. An operon is a region of DNA that codes for sugar-metabolizing enzymes.
C. An operon is a region of RNA that consists of the coding regions of more than one gene.
D. An operon is a region of DNA that codes for a series of functionally related genes under the control of the same promoter.
E. an operon is a region of DNA that codes for exons and introns, which are then spliced to produce appropriate and specific mRNAs.
D
When a stop codon on a mRNA reaches the “A” site in a ribosome,
A. one of four tRNAs that are associated with the stop codon will bind at the “A” site
B. a single, special tRNA lacking an amino acid will bind at the “A” site
C. a special protein factor will fill the “A” site
D. double stranded mRNA will bind at the “A” site
E. a hairpin loop will form in the mRNA
C
A compound known as X-Gal is widely used in molecular genetic research. When wild-type (normal) E. coli is grown on medium containing X-Gal, the bacterial colonies turn blue. In contrast, when lacZ mutants are grown on medium containing X-Gal, the bacterial colonies remain their normal white color. What is X-Gal likely to be?
A. a compound that can only be transported into lacA mutants
B. a compound chemically similar to glucose
C. a compound chemically similar to galactose
D. a compound chemically similar to lactose
E. a compound that cannot be transported into lacZ mutants
D
The anti-codon portion of the tRNA
A. Binds to the amino acid being transferred
B. Is essential in forming the alpha helix structure of tRNA
C. Associates with the complementary base pairs on mRNA
D. Was found to be radioactively labeled by researchers using cell-free preparations to examine protein synthesis
E. Binds to the enzyme that activates an amino acid to produce an aminoacyl tRNA
C
Which of the following have a site that binds specific regulatory proteins that promote highly specific gene transcription?
A. exons B. introns C. promoter sequences D. proximal promoter element sites E. enhancer regions
D
The RNA segments joined to one another by spliceosomes are _____.
A. Caps B. exons C. tails D. introns E. enhancers
B
Which types of mutants did Jacob and Monad come across in their studies of gene regulation?
A. mutations that prevented the expression and function of B-galactosidase
B. mutations that prevented the expression and function of galactoside permease
C. mutations that prevented the expression and function of the regulatory protein that controls expression of other genes
D. all of the above
E. none of the above
D
What kind of gene regulation is perceived as being particularly efficient but relatively slow in prokaryotes?
A. synthesis of DNA B. transcriptional control C. translational control D. post-translational control E. appropriate splicing of exons and introns
B
Codons are three-base sequences that specify the addition of a single amino acid. How do eukaryotic codons and prokaryotic codons compare?
A. The translation of codons is mediated by tRNAs in eukaryotes, but translation requires no intermediate molecules such as tRNAs in prokaryotes.
B. Codons are a nearly universal language among all organisms.
C. Prokaryotic codons usually specify different amino acids than those of eukaryotes.
D. Prokaryotic codons usually contain different bases than those of eukaryotes
E. Eukaryotic codons are much more complex than prokaryotic codons.
B
An example of a basal transcription factor is
A. RNA ppolymerase
B. the TATA binding protein
C. a promoter-proximal-binding transcription factor
D. a silencer-binding transcription factor
E. an enhancer-binding transcription factor
A
Lactose binds to _____ and causes _____
A. bindin; increased production of cAMP
B. repressor protein; allosteric regulation
C. B-galactosidase; increased gene expression of genes in the lac operon
D. galactoside permease; dereased gene expression of genes in the lac operon
E. glucose; decreased production of cAMP
B
When arabinose is present and glucose is absent,
A. the ara operon will be turned on by positive control
B. the ara operon will be turned on by negative control
C. the ara operon will be turned off by positive control
D. the ara operon will be turned off by negative control
E. the ara operon will first turn on and then turn off
A
Although the expression of most genes is tightly regulated, some genes are expressed at roughly constant rates (i.e., constitutively). Which of the following genes would you predict to be constitutively expressed?
A. genes involved in the transport of the sugar maltose
B. genes involved in the degradation of arabinose, a sugar
C. genes involved in the degradation of lactose
D. genes that code for ribosomal RNAs
E. genes involved in the synthesis of lactose
D
When we say that the genetic code is redundant, what is meant?
A. A single codon never specifies more than one amino acid
B. With a few minor exceptions, all codons specify the same amino acids in all organisms
C. When several codons specify the same amino acid, the first two bases are almost always identical
D. All amino acids except methionine and tryptophan are coded for by more than one codon
E. Codons can be cut out of mRNAs to allow new amino acids to be inserted
D
During RNA processing a(n) _____ is added to the 3’ end of the RNA.
A. 3' untranslated region B. a long string of adenine nucleotides C. 5' untranslated region D. coding segment E. intron
B
During transcription, in which direction is (1) RNA synthesized and in which direction is (2) the DNA template “read”?
A. (1) 5'—>3' (2) 5'—>3' B. (1) 3'—>5' (2) 5'—>3' C. (1) 5'—>3' (2) 3'—>5' D. (1) 3'—>5' (2) 3'—>5' E. (1) 5'—>5' (2) 3'—>3'
C
A promoter is
A. a special part of the RNA molecule
B. a site in DNA that recruits an RNA polymerase
C. a protein that binds to the DNA
D. a protein that binds to the RNA polymerase
E. a protein that binds to RNA
B
An experimenter wishes to determine the length of the S phase of liver cells. Which of the following compounds might be useful in determining this property?
A. thymidine B. adenosine C. uracil D. cytosine E. guanosine
A
According to the article “Is most of our DNA garbage”, what does Dr. T. Ryan Gregory say about most of our DNA?
A. It is mostly junk
B. Most is critical to producing RNAi and turning on genes
C. Most is critical to producing RNAi and turning off genes
D. Most is critical to the production of mRNAs
E. Most are shuffled exons waiting to be expressed in the right circumstances
A
According to the article “The Second Coming of RNAi”, approximately when was RNAi first discovered?
A. “It simply won’t be possible to do this with siRNA”
B. “While theoretically possible, we are many years away from being able to treat Ebola with siRNA”
C. “We are currently dealing with the harmful side effects of siRNA in the use of Ebola infections. It is difficult to separate cure from disease”.
D. “We have been able to establish in animal models that we can rescue the animals from certain death following an Ebola infection”.
D
The reason for differences in the sets of proteins expressed in a nerve and a pancreatic cell of the same individual is that nerve and pancreatic cells contain different _____.
A. genes B. promotors C. regulatory sequences D. sets of regulatory proteins E. promotor proximal elements
D
Are histone deacetylases (HDACs) associated with negative or positive control of gene expression? Why?
A. negative control, because they make DNA less accessible for transcription
B. positive control, because they make mRNA more accessible for translation
C. negative control, because they make mRNA less accessible for translation
D. positive control, because they make DNA more accessible for transcription
E. positive and negative control, because they generally sometimes make DNA less accessible and sometimes make it more accessible.
A
Which of the following is most critical for the association between histones and DNA?
A. Histones are highly conserved (i.e., histones are very similar in every eukaryote).
B. Histones are small proteins
C. Histones are synthesized in the cytoplasm.
D. Histones are positively charged.
E. There are at least five different histone proteins in every eukaryote.
D
In eukaryotes, TATA sites can typically be found in
A. exons B. introns C. promoter sequences D. proximal promotor element sites E. enhancer regions
C
The advantage of having exons and introns is that
A. expression of proteins can be significantly enhanced
B. it is easy to degrade mRNA signals
C. a very large number of variant proteins can be made from a single gene
D. enhancers and silencers can be used to regulate gene transcription
E. translation can be halted quickly
C
Scientists isolate cells in various phases of the cell cycle. They find a group of cells that have 1½ times more DNA than do G1 phase cells. The cells of this group are _____.
A. between the G1 and S phases in the cell cycle B. in the M phase of the cell cycle C. in the G1 phase of the cell cycle D. in the S phase of the cell cycle E. in the G2 phase of the cell cycle
D
The phenomenon in which RNA molecules in a cell are destroyed if they have a sequence complementary to an introduced double-stranded RNA is called
A. RNA blocking B. RNA targeting C. RNA obstruction D. RNA operons E. RNA interference
E
Imagine that you’ve discovered a regulatory sequence thousands of base pairs away from the promoter and that when this sequence is lost due to mutation, levels of gene expression decrease sharply. This sequence is most likely
A. an enhancer B. a silencer C. a promotor D. a promotor-proximal element E. an operon
A
