Chapter 17 and 18 Mastering Biology: Test Answers

dna methylation and histone acetylation are examples of which of the following processes?

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Gene expression is often assayed by measuring the level of mRNA produced from a gene. What level of the control of gene expression can by analyzed by this type of assay?
transcriptional control
Which statements about the modification of chromatin structure in eukaryotes are true?
Some forms of chromatin modification can be passed on to future generations of cells.
Acetylation of histone tails is a reversible process.
DNA is not transcribed when chromatin is packaged tightly in a condensed form.
Acetylation of histone tails in chromatin allows access to DNA for transcription.
Methylation of histone tails in chromatin can promote condensation of the chromatin.
Which statements about the regulation of transcription initiation in these genes are true?

Control elements C, D, and E are distal control elements for the imaginin gene.

The fantasin gene will be transcribed at a high level when activators specific for control elements A, B, and C are present in the cell.

Both the fantasin gene and the imaginin gene will be transcribed at high levels when activators specific for control elements A, B, C, D, and E are present in the cell.

Which of the following choices represent mRNA molecules that could be produced from the primary RNA transcript by alternative RNA splicing? (In each choice, the yellow part on the left represents the 5′ cap, and the yellow part on the right represents the poly-A tail.)
ACGI
ACEGI
ACEIAlternative RNA splicing produces different mRNA molecules from the same primary RNA transcript. During alternative RNA splicing, all introns are removed, and some exons may also be removed. The removal of different exons produces different mRNA molecules, which are then translated into different proteins. Alternative RNA splicing can greatly expand the number of proteins produced from the same gene.
Which of the following would be most likely to lead to cancer?

amplification of a proto-oncogene and inactivation of a tumor-suppressor gene

Excess copies of the proto-oncogene could stimulate cell division abnormally, and the inactivation of a tumor-suppressor gene would eliminate a brake on cell division.

Which of the following processes do normal proto-oncogenes typically exhibit?
They stimulate normal cell growth and division.
Which of the following statements correctly describes a characteristic of tumor-suppressor gene?
They encode proteins that help prevent uncontrolled cell growth.
Forms of the Ras protein found in tumors usually cause which of the following events to occur?
excess cell division
_____ bind(s) to DNA enhancer regions.

Activators

Activators are a type of transcription factor that bind to enhancer regions.

What is the event that IMMEDIATELY follows the last event of this animation?
binding of RNA polymerase to the promoter
Which of these indicates an enhancer region?
Which of these indicates an enhancer region?
A
Which of these directly bind(s) to the promoter?
Which of these directly bind(s) to the promoter?
C and D
Both RNA polymerase and transcription factors bind with the promoter.
Which of the following terms describes the DNA-protein complexes that look like beads on a string?
nucleosome
Which of the following regulatory elements is not composed of DNA sequences?
Activators
True or false? Regulatory and basal transcription factors regulate transcription by binding to the promoter.

False

Basal transcription factors do indeed bind to the promoter, but regulatory transcription factors bind to promoter-proximal elements and enhancers.

Which of the following regulatory DNA sequences might be located thousands of nucleotides away from the transcription start site of a gene?

enhancer

Enhancers can function thousands of nucleotides away from the promoter and transcription start site.

Which of the following events in transcription initiation likely occurs last?

RNA polymerase binds to the promoter of the gene

RNA polymerase is recruited only when other transcription factors, including TBP, are assembled at the promoter.

True or false? One possible way to alter chromatin structure such that genes could be transcribed would be to make histone proteins more positively charged

False

The positive charge on histone proteins allows them to interact tightly with negatively charged DNA, thus inhibiting transcription. To disrupt this interaction, the histone proteins would have to be made more negatively charged.

DNA methylation is a mechanism used by eukaryotes to do what?

inactivate genes

DNA methylation, involving the attachment of methyl groups to certain bases, is a mechanism for the long-term inactivation of genes during development

It is possible for a cell to make proteins that last for months; hemoglobin in red blood cells is a good example. However, many proteins are not this long-lasting; they may be degraded in days, hours, or even minutes. What is the advantage of short-lived proteins?
Short-lived proteins enable the cells to control their activities precisely and efficiently.
Which of the following mechanisms is used to coordinate the expression of multiple, related genes in eukaryotic cells?
A given gene may have multiple enhancers, but each enhancer is generally associated with only that gene and no other.
DNA methylation and histone acetylation are examples of which of the following processes?
epigenetic phenomena
A high concentration of bicoid protein at the opposite ends of a developing Drosophila embryo would result in the development of a _____.
two headed fly
The bicoid gene product is directly responsible for _____ in a developing Drosophila embryo.
the establishment of the anterior-posterior axis
The region of a Drosophila embryo with the highest concentration of bicoid protein will develop into the _____.
head
What triggers the translation of bicoid mRNA?
fertilization of the egg
The bicoid gene is a type of _____ gene.
egg-polarity
The region of a Drosophila embryo with a low concentration of bicoid protein will develop into the _____.
abdomen
What process produces the gradient of bicoid protein in a fertilized egg?
diffusion
Bicoid mRNA is translated in _____.
fertilized egg
The bicoid gene is transcribed by _____.
nurse cells
Which of these is true of the cytoplasm of an unfertilized egg?
It is an unevenly distributed mixture of mRNA, proteins, organelles, and other substances.
How do master regulatory genes function in cell differentiation?
They produce proteins that act as transcription factors to produce proteins specific to the function of the particular cell type.
They are often capable of changing some fully differentiated cells of different types into their particular cell type.
They may produce proteins that stimulate production of more of the master regulatory gene.
The transcription factors they produce coordinately control related genes.
What name is given to the process in which a strand of DNA is used as a template for the manufacture of a strand of pre-mRNA?
transcription
What name is given to the process in which the information encoded in a strand of mRNA is used to construct a protein?
translation
v
RNA processing
Polypeptides are assembled from _____.
amino acids
RNA processing converts the RNA transcript into _____.
mRNA
A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.
three… amino acids
A particular triplet of bases in the template strand of DNA is 5-AGT-3. What would be the corresponding codon for the mRNA that is transcribed?
3-UCA-5
Which of the following sequences of nucleotides are possible in the template strand of DNA that would code for the polypeptide sequence Phe-Leu-Ile-Val?
Which of the following sequences of nucleotides are possible in the template strand of DNA that would code for the polypeptide sequence Phe-Leu-Ile-Val?
3-AAA-GAA-TAA-CAA-5
Refer to the figure. Which of the triplets below is a possible anticodon for a tRNA that transports proline to a ribosome?
Refer to the figure. Which of the triplets below is a possible anticodon for a tRNA that transports proline to a ribosome?
3-GGC-5
What amino acid sequence will be generated, based on the following mRNA codon sequence? 5-AUG-UCU-UCG-UUA-UCC-UUG-3
What amino acid sequence will be generated, based on the following mRNA codon sequence?
5-AUG-UCU-UCG-UUA-UCC-UUG-3
Met-Ser-Ser-Leu-Ser-Leu
What is the process called that converts the genetic information stored in DNA to an RNA copy?
transcription
DNA does not store the information to synthesize which of the following?
organelles
Transcription begins at a promoter. What is a promoter?
A site in DNA that recruits the RNA Polymerase
Which of the following statements best describes the promoter of a protein-coding gene?
The promoter is a nontranscribed region of a gene
What determines which base is to be added to an RNA strand during transcription?
between the DNA template strand and the RNA nucleotides
Which of the following terms best describes the relationship between the newly synthesized RNA molecule and the DNA template strand?
complementary
What happens to RNA polymerase II after it has completed transcription of a gene?
It is free to bind to another promoter and begin transcription
The direction of synthesis of an RNA transcript is _____.
5′ –> 3′
Transcription in eukaryotes requires which of the following molecules in addition to RNA polymerase?
several transcription factors
Which of the following statements best describes the termination of transcription in prokaryotes?
RNA polymerase transcribes through the terminator sequence, causing the polymerase to separate from the DNA and release the transcript.
During RNA processing a(n) _____ is added to the 5′ end of the RNA.
modified guanine nucleotide
During RNA processing a(n) _____ is added to the 3′ end of the RNA.
a long string of adenine nucleotides
Spliceosomes are composed of _____.
small RNAs and proteins
The RNA segments joined to one another by spliceosomes are _____.
exons
Translation occurs in the _____.
cytoplasm
What is a ribozyme?
a biological catalyst made of RNA
Which of the following processes occurs in eukaryotic gene expression?
A cap is added to the 5 end of the mRNA
Which of the following processes correctly describes alternative RNA splicing?
It can allow the production of proteins of different sizes and functions from a single mRNA.
In the structural organization of many eukaryotic genes, individual exons may be related to which of the following?
the various domains of the polypeptide product
How does the primary transcript in the nucleus of a eukaryotic cell compare to the functional mRNA?
the primary transcript is larger than the mRNA
How does the primary transcript in a prokaryotic cell compare to the functional mRNA?
the primary transcript is the same size as the mRNA
Where does translation take place?
ribosome
Which nucleic acid is translated to make a protein?
mRNA
Which of the following processes is an example of a post-translational modification?
phosphorylation
Which of the following steps occurs last in the initiation phase of translation?
The large ribosomal subunit joins the complex
At which site do new aminoacyl tRNAs enter the ribosome during elongation?
A site
What is meant by translocation?
The ribosome slides one codon down the mRNA.
True or false. A tRNA with an anticodon complementary to the stop codon catalyzes the reaction by which translation is terminated.

False

There are no tRNAs complementary to the three stop codons; termination occurs when release factors recognize the stop codon in the A-site and catalyze the release of the polypeptide from the tRNA in the P-site

Which of these is tRNA
Which of these is tRNA
B
What enzyme catalyzes the attachment of an amino acid to tRNA?
aminoacyl-tRNA synthetase
The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____.
CUG
initiation of translation
initiation of translation
The initiator tRNA attaches at the ribosome’s _____ site.
P
The tRNA transfers an amino acid to the growing polypeptide chain. It is a molecule involved in translation of mRNA.
Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in the _____.
binding of the anticodon to the codon and the attachment of amino acids to tRNAs
Which of the following processes is the first event to take place in translation in eukaryotes?
the small subunit of the ribosome recognizes and attaches to the 5 cap of mRNA
What is the function of the release factor during translation in eukaryotes?
It binds to the stop codon in the A site in place of a tRNA
What type of bonding is responsible for maintaining the shape of the tRNA molecule shown in the figure?
hydrogen bonding between base pairs
During the elongation phase of translation, which site in the ribosome represents the location where a codon is being read?
A site
Which of the following processes occurs when termination of translation takes place?
a stop codon is reached
True or false? A codon is a group of three bases that can specify more than one amino acid.

False

a codon is a group of three bases that can specify only one amino acid

A knock-out mutation refers to the loss of a protein’s function but not necessarily to its complete absence.
Which of the following statements about mutations is false?
1.A knock-out mutation results in a total absence of the mutated protein.
2.An addition mutation results in an added base in the DNA sequence.
3.Addition and deletion mutations disrupt the primary structure of proteins.
4. A deletion mutation results in the loss of a base in the DNA sequence.
1
If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?
deletion
Which mutation(s) would not change the remainder of the reading frame of a gene sequence that follows the mutation(s)?
One addition and one deletion mutation.
If the sequence ATGCATGTCAATTGA were mutated such that a base were inserted after the first G and the third T were deleted, how many amino acids would be changed in the mutant protein?
two
If a mutated DNA sequence produces a protein that differs in one central amino acid from the normal protein, which of the following kinds of mutations could have occurred?
an addition mutation and a deletion mutation
Think about the DNA coding sequence of a gene. If an A were swapped for a T, what kind of mutation could it cause and why?
It could cause a silent, missense, or nonsense mutation because those are the types that can be caused by a nucleotide-pair substitution like this one.
Why is a frameshift missense mutation more likely to have a severe effect on phenotype than a nucleotide-pair substitution missense mutation in the same protein?
A substitution missense affects only one codon, but a frameshift missense affects all codons downstream of the frameshift.
Which of the following sequences shows a frameshift mutation compared to the wild-type mRNA sequence?
wild-type 5′-AUGCAUACAUUGGAGUGA-3′
mutant 5′-AUGCAUACAUCUGGAGUGA-3′
A________ does not change the wild-type amino acid sequence.
silent mutation
A _____ mutation causes a wild-type amino acid to be replaced by a different amino acid
missense
A ______mutation causes an early Stop codon to occur.
nonsense
Suppose that the triplet of nucleotides indicated in bold (AGC) spans two codons, that is, CTA and GCC. If the triplet AGC were deleted from this DNA coding sequence, what effect would it have on the resulting protein?
5′-ATGCTAGCCTATCGTAAC-3′
The two flanking codons would be altered, but the rest of the amino acid sequence would be the same because there would be no frameshift.
Which of the following statements correctly describes the effect a nonsense mutation would have on a gene?
It introduces a premature stop codon into the mRNA.
The most commonly occurring mutation in people with cystic fibrosis is a deletion of a single codon. What is the result of this type of mutation?
polypeptide missing an amino acid
Which of the following statements is the most current description of a gene?
a DNA sequence that is expressed to form a functional product: either RNA or polypeptide
Which of the following molecules are produced by transcription?
ribozymes and messenger RNA
Which of the following molecules is/are produced by translation? Include molecules that are subject to further modification after initial synthesis.
RNA polymerase
Aminoacyl-tRNA synthetase

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