Chapter 17 And 18 Mastering Biology: Test Answers

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?

ANSWER : transcriptional control

Which statements about the modification of chromatin structure in eukaryotes are true?

ANSWER : 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?

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

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.)

ANSWER : 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?

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

Which of the following processes do normal proto-oncogenes typically exhibit?

ANSWER : They stimulate normal cell growth and division.

Which of the following statements correctly describes a characteristic of tumor-suppressor gene?

ANSWER : 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?

ANSWER : excess cell division

_____ bind(s) to DNA enhancer regions.

ANSWER : Activators

What is the event that IMMEDIATELY follows the last event of this animation?

ANSWER : binding of RNA polymerase to the promoter

Which of these indicates an enhancer region?

ANSWER : A

Which of these directly bind(s) to the promoter?

ANSWER : 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?

ANSWER : nucleosome

Which of the following regulatory elements is not composed of DNA sequences?

ANSWER : Activators

True or false? Regulatory and basal transcription factors regulate transcription by binding to the 

promoter.

ANSWER : FALSE

Which of the following regulatory DNA sequences might be located thousands of nucleotides away from 

the transcription start site of a gene?

ANSWER : enhancer

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

ANSWER : RNA polymerase binds to the promoter of the gene

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

ANSWER : FALSE

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

ANSWER : inactivate genes

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?

ANSWER : 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?

ANSWER : 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?

ANSWER : epigenetic phenomena

A high concentration of bicoid protein at the opposite ends of a developing Drosophila embryo would 

result in the development of a _____.

ANSWER : two headed fly

The bicoid gene product is directly responsible for _____ in a developing Drosophila embryo.

ANSWER : the establishment of the anterior-posterior axis

The region of a Drosophila embryo with the highest concentration of bicoid protein will develop into the 

_____.

ANSWER : head

What triggers the translation of bicoid mRNA?

ANSWER : fertilization of the egg

The bicoid gene is a type of _____ gene.

ANSWER : egg-polarity

The region of a Drosophila embryo with a low concentration of bicoid protein will develop into the 

_____.

ANSWER : abdomen

What process produces the gradient of bicoid protein in a fertilized egg?

ANSWER : diffusion

Bicoid mRNA is translated in _____.

ANSWER : fertilized egg

The bicoid gene is transcribed by _____.

ANSWER : nurse cells

Which of these is true of the cytoplasm of an unfertilized egg?

ANSWER : It is an unevenly distributed mixture of mRNA, proteins, organelles, and other substances.

How do master regulatory genes function in cell differentiation?

ANSWER : 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?

ANSWER : transcription

What name is given to the process in which the information encoded in a strand of mRNA is used to 

construct a protein?

ANSWER : translation

v

ANSWER : RNA processing

Polypeptides are assembled from _____.

ANSWER : amino acids

RNA processing converts the RNA transcript into _____.

ANSWER : mRNA

A codon consists of _____ bases and specifies which _____ will be inserted into the polypeptide chain.

ANSWER : 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?

ANSWER : 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?

ANSWER : 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?

ANSWER : 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

ANSWER : Met-Ser-Ser-Leu-Ser-Leu

What is the process called that converts the genetic information stored in DNA to an RNA copy?

ANSWER : transcription

DNA does not store the information to synthesize which of the following?

ANSWER : organelles

Transcription begins at a promoter. What is a promoter?

ANSWER : A site in DNA that recruits the RNA Polymerase

Which of the following statements best describes the promoter of a protein-coding gene?

ANSWER : The promoter is a nontranscribed region of a gene

What determines which base is to be added to an RNA strand during transcription?

ANSWER : 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?

ANSWER : complementary

What happens to RNA polymerase II after it has completed transcription of a gene?

ANSWER : It is free to bind to another promoter and begin transcription

The direction of synthesis of an RNA transcript is _____.

ANSWER : 5′ –> 3′

Transcription in eukaryotes requires which of the following molecules in addition to RNA polymerase?

ANSWER : several transcription factors

Which of the following statements best describes the termination of transcription in prokaryotes?

ANSWER : 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.

ANSWER : modified guanine nucleotide

During RNA processing a(n) _____ is added to the 3′ end of the RNA.

ANSWER : a long string of adenine nucleotides

Spliceosomes are composed of _____.

ANSWER : small RNAs and proteins

The RNA segments joined to one another by spliceosomes are _____.

ANSWER : exons

Translation occurs in the _____.

ANSWER : cytoplasm

What is a ribozyme?

ANSWER : a biological catalyst made of RNA

Which of the following processes occurs in eukaryotic gene expression?

ANSWER : A cap is added to the 5 end of the mRNA

Which of the following processes correctly describes alternative RNA splicing?

ANSWER : 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?

ANSWER : the various domains of the polypeptide product

How does the primary transcript in the nucleus of a eukaryotic cell compare to the functional mRNA?

ANSWER : the primary transcript is larger than the mRNA

How does the primary transcript in a prokaryotic cell compare to the functional mRNA?

ANSWER : the primary transcript is the same size as the mRNA

Where does translation take place?

ANSWER : ribosome

Which nucleic acid is translated to make a protein?

ANSWER : mRNA

Which of the following processes is an example of a post-translational modification?

ANSWER : phosphorylation

Which of the following steps occurs last in the initiation phase of translation?

ANSWER : The large ribosomal subunit joins the complex

At which site do new aminoacyl tRNAs enter the ribosome during elongation?

ANSWER : A site

What is meant by translocation?

ANSWER : 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.

ANSWER : FALSE

Which of these is tRNA

ANSWER : B

What enzyme catalyzes the attachment of an amino acid to tRNA?

ANSWER : aminoacyl-tRNA synthetase

The tRNA anticodon, GAC, is complementary to the mRNA codon with the sequence _____.

ANSWER : CUG

initiation of translation

ANSWER : 

The initiator tRNA attaches at the ribosome’s _____ site.

ANSWER : P

The tRNA transfers an amino acid to the growing polypeptide chain. It is a molecule involved in 

translation of mRNA.

ANSWER : 

Accuracy in the translation of mRNA into the primary structure of a polypeptide depends on specificity in 

the _____.

ANSWER : 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?

ANSWER : 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?

ANSWER : 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?

ANSWER : 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?

ANSWER : A site

Which of the following processes occurs when termination of translation takes place?

ANSWER : a stop codon is reached

True or false? A codon is a group of three bases that can specify more than one amino acid.

ANSWER : FALSE

A knock-out mutation refers to the loss of a protein’s function but not necessarily to its complete 

absence.

ANSWER : 

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.

ANSWER : 1

If a DNA sequence is altered from TAGCTGA to TAGTGA, what kind of mutation has occurred?

ANSWER : deletion

Which mutation(s) would not change the remainder of the reading frame of a gene sequence that 

follows the mutation(s)?

ANSWER : 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?

ANSWER : 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?

ANSWER : 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?

ANSWER : 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?

ANSWER : 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?

ANSWER : wild-type 5′-AUGCAUACAUUGGAGUGA-3′ mutant 5′-AUGCAUACAUCUGGAGUGA-3′

A________ does not change the wild-type amino acid sequence.

ANSWER : silent mutation

A _____ mutation causes a wild-type amino acid to be replaced by a different amino acid

ANSWER : missense

A ______mutation causes an early Stop codon to occur.

ANSWER : 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′

ANSWER : 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?

ANSWER : 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?

ANSWER : polypeptide missing an amino acid

Which of the following statements is the most current description of a gene?

ANSWER : a DNA sequence that is expressed to form a functional product: either RNA or polypeptide

Which of the following molecules are produced by transcription?

ANSWER : 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.

ANSWER : RNA polymerase Aminoacyl-tRNA synthetase