In eukaryotic cells, transcription cannot begin until __________.

the two DNA strands have completely separated and exposed the promoter
the 5′ caps are removed from the mRNA
the DNA introns are removed from the template
several transcription factors have bound to the promoter
DNA nucleases have isolated the transcription unit

d
Which of the following is NOT true of a codon?

It may code for the same amino acid as another codon.
It extends from one end of a tRNA molecule.
It is the basic unit of the genetic code.
It consists of three nucleotides.
It never codes for more than one amino acid.

b
The anticodon of a particular tRNA molecule is __________.

changeable, depending on the amino acid that attaches to the tRNA
complementary to the corresponding triplet in rRNA
complementary to the corresponding mRNA codon
catalytic, making the tRNA a ribozyme
the part of tRNA that bonds to a specific amino acid

c
Which of the following is NOT true of RNA processing?

Ribozymes may function in RNA splicing.
A primary transcript is often much longer than the final RNA molecule that leaves the nucleus.
Nucleotides may be added at both ends of the RNA.
RNA splicing can be catalyzed by spliceosomes.
Exons are cut out before mRNA leaves the nucleus.

e
Which component is NOT directly involved in translation?

tRNA
GTP
DNA
mRNA
ribosomes

c
Which of the following mutations would be most likely to have a harmful effect on an organism?

a single nucleotide deletion near the end of the coding sequence
a single nucleotide insertion downstream of, and close to, the start of the coding sequence
a nucleotide-pair substitution
a single nucleotide deletion in the middle of an intron
a deletion of three nucleotides near the middle of a gene

b
Who formulated the one gene-one enzyme hypothesis? (eText Concept 14.1)

Watson and Crick
Beadle and Tatum
Hershey and Chase
Franklin
None of the listed responses is correct.

b
Genetic information of eukaryotic cells is transferred from the nucleus to the cytoplasm in the form of _____. (eText Concept 14.1)

proteins
lipids
RNA
carbohydrates
DNA

c
Which of the following statements is true? (eText Concept 14.1)

Each DNA base codes for three amino acids.
Each gene codes for three proteins.
It takes three genes to code for one protein.
Each triplet has many different meanings.
Each amino acid in a protein is coded for by three bases in the DNA.

e
When RNA is being made, the RNA base _____ always pairs with the base _____ in DNA. (eText Concept 14.1)

U … T
T … G
U … A
A … U
T … A

c
Generally speaking, how many genetic codes are there? (eText Concept 14.1)

20
one
four
one for each organism
three

b
What mRNA codon would be made from the DNA triplet CGT? (eText Concept 14.1)

ATU
GCA
TCU
CTA
UCG

b
The number of nucleotide bases “read” together on the mRNA to designate each amino acid is _____; this unit is called a(n) _____. (eText Concept 14.1)

two … dipeptide
three … triose
two … anticodon
three … codon
one … amino acid

d
The codons AAA, CCC, GGG, and UUU specify the amino acids lysine, proline, glycine, and phenylalanine, respectively. What peptide sequence would be encoded by the sequence 5′-CCCAAATTTGGG-3′, if present in the coding strand of the DNA? (eText Concept 14.1)

lys-pro-gly-phe
pro-lys-phe-gly
gly-phe-lys-pro
phe-gly-pro-lys
gly-phe-pro-lys

b
How many nucleotides are needed to code for a protein with 450 amino acids? (eText Concept 14.1)

at least 150
at least 300
at least 450
at least 900
at least 1,350

e
In many cases, more than one codon codes for the same amino acid. Because of this, we say that the code is _____. (eText Concept 14.1)

inaccurate
incomplete
not specific
redundant
tricky

d
Bacteria can transcribe and translate human genes to produce functional human proteins because _____. (eText Concept 14.1)

the genetic code is nearly universal
bacterial ribosomes and eukaryotic ribosomes are identical
eukaryotes do not really need a nucleus
RNA has catalytic properties
bacterial and eukaryotic RNA polymerases are identical

a
In a eukaryotic cell, transcription takes place _____. (eText Concept 14.1)

on the cell membrane
in the rough endoplasmic reticulum
in the cytoplasm
on free ribosomes
in the nucleus

e
Which of the following best describes the arrangement of genetic information in a DNA molecule? (eText Concept 14.1)

A gene is composed of overlapping, three-nucleotide words on a template strand of DNA.
The three-nucleotide words of a gene are serially arranged on both strands of DNA at a specific locus.
The three-nucleotide words of a gene are arranged in a nonoverlapping series on the DNA template strand.
By overlapping the three-nucleotide words of a gene, the amount of information a DNA molecule can hold is maximized.
By analyzing the linear order of amino acids in a polypeptide, the exact order of the three-nucleotide words of a gene arranged on the template strand of DNA can be determined.

c
At one point, as a cell carried out its day-to-day activities, the nucleotides GAT were paired with the nucleotides CUA. This pairing occurred _____. (eText Concept 14.2)

in a double-stranded DNA molecule
during translation
during transcription
when an mRNA codon paired with a tRNA anticodon
It is impossible to say, given this information.

c
Which of the following catalyzes the linkage between ribonucleotides to form RNA during gene expression? (eText Concept 14.2)

RNA polymerase
RNA ligase
a ribozyme
reverse transcriptase
tRNA

a
One strand of a DNA molecule has the following sequence: 3′-AGTACAAACTATCCACCGTC-5′. In order for transcription to occur in that strand, there would have to be a specific recognition sequence, called a(n) _____, to the left of the DNA sequence indicated. (eText Concept 14.2)

centromere
intron
exon
AUG codon
promoter

e
During the transcription of a given portion of a DNA molecule _____. (eText Concept 14.2)

mRNA is synthesized on both chains of the DNA molecule at once
mRNA is synthesized on both chains of the DNA molecule, but first on one side and then the other
mRNA is synthesized on only one of the chains
half of the mRNA is synthesized on half of one chain; then the other half of the mRNA is made on the other half of the DNA
Any of the listed patterns may be found.

c
In transcription, _____. (eText Concept 14.2)

the promoter region acts as an initial binding site for RNA polymerase
only one of the DNA strands is used as the template
the RNA nucleotides used are produced by the cell
All of the listed responses are correct.
None of the listed responses is correct.

d
Which of the following statements is false?(eText Concept 14.2)

In bacteria, proteins called transcription factors enhance the affinity of RNA polymerase to the promoter sites of genes.
In bacteria, transcription of a gene is initiated when the RNA polymerase by itself recognizes and binds to the promoter of the gene.
The initiation of gene transcription in eukaryotes requires the binding of proteins called transcription factors to the TATA box in the promoter region of a gene.
A relaxation of chromatin packing in eukaryotic cells can facilitate the binding of transcription factors to a promoter of a gene.
All of the listed responses are correct.

a
In eukaryotes, which of the following mechanisms of gene regulation operates after transcription, but before translation of mRNA into protein? (eText Concept 14.3)

RNA splicing
DNA packaging into nucleosomes
action of repressors and activators
protein degradation
All of the listed responses are correct.

a
Which of the following accurately describes the usual process of transcription for eukaryotic genes? (eText Concept 14.3)

Exons are not transcribed.
Introns are not transcribed.
Exons are transcribed, but the RNA transcribed from introns does not leave the nucleus.
Both introns and exons are transcribed, but the RNA transcribed from them does not leave the nucleus.
Exons and introns are transcribed, and the RNA transcribed from them leaves the nucleus.

c
Which of the following statements correctly describes mRNA processing? (eText Concept 14.3)

Introns are cut out of the primary transcript, and the resulting exons are spliced together.
Exons are cut out of the primary transcript, and the introns are spliced together.
Introns are cut out of the primary transcript and spliced together at the end of the transcript.
Exons are cut out of the primary transcript and transported to the endoplasmic reticulum.
Introns are cut out of the primary transcript and transported to the ribosomes.

a
A cell biologist found that two different proteins with largely different structures were translated from two different mRNAs. These mRNAs, however, were transcribed from the same template within the cell nucleus. Which mechanism below could best account for this? (eText Concept 14.3)

Different systems of DNA unpacking could result in two different mRNAs.
A point mutation might have altered the gene.
Exons from the same gene could be spliced in different ways to make different mRNAs.
Different transcription factors were involved in the transcription of the two mRNAs.
The two proteins have different functions in the cell.

c
The function of tRNA during protein synthesis is to _____. (eText Concept 14.4)

deliver amino acids to their proper site during protein synthesis
guide ribosome subunits out of the nucleus through nuclear pores
attach mRNA to the small subunit of the ribosome
process mRNA
transcribe mRNA

a
Which of the following summaries of protein synthesis is correct? (eText Concept 14.4)

DNA transposons leave the nucleus, are transported to a ribosome, and catalyze the polymerization of amino acids in a protein.
DNA exchanges its thymine units with uracil in polymerase. This activates polymerase, and it starts joining amino acids together.
Transfer RNAs line up on a ribosome, and amino acids bind to them with hydrogen bonds.
Messenger RNA is made on a DNA template, and then amino-acid-bearing transfer RNAs bind to it through codon-anticodon pairing.
DNA strands separate in the nucleus to form mRNA. mRNA leaves the nucleus and is transcribed into tRNA on ribosomes.

d
The bonds that hold tRNA molecules in the correct three-dimensional shape are _____. (eText Concept 14.4)

peptide linkages
hydrophobic interactions
covalent bonds
ionic bonds
hydrogen bonds

e
During translation in a eukaryotic cell _____. (eText Concept 14.4)

ribosomes move into the nucleus
tRNA carries amino acid molecules to the nucleus, where they are added to a growing polypeptide chain
polypeptides are synthesized at ribosomes, according to instructions carried by mRNA
mRNA is synthesized by the bonding of free nucleotides to the bases on the template strand of DNA
ribosomes move out of the nucleus

c
The P site of a ribosome does which of the following? (eText Concept 14.4)

It holds the tRNA that is carrying the next amino acid to be added to the growing polypeptide chain.
It holds the tRNA carrying the growing polypeptide chain.
It helps “unzip” DNA during transcription.
It catalyzes the addition of amino acids to the tRNAs.
It recognizes the promoter during transcription initiation.

b
The first amino acid inserted into a new polypeptide chain in eukaryotic cells is usually _____. (eText Concept 14.4)

glycine
serine
methionine
adenosine monophosphate
alanine

c
Which of the following is a post-translational modification of a polypeptide? (eText Concept 14.4)

cleavage of a polypeptide into two or more chains
removal of introns and splicing of exons
formation of a polysome that allows simultaneous formation of many polypeptides from one mRNA transcript
The growing polypeptide signals the ribosome to attach to the ER.
complementary base pairing of mRNA and tRNA in the ribosome

a
During translation, amino acid chain elongation occurs until _____. (eText Concept 14.4)

no further amino acids are needed by the cell
all tRNAs are empty
the polypeptide is long enough
the ribosome encounters a “stop” codon
the ribosome runs off the end of the mRNA strand

d
Polysomes may be defined as _____. (eText Concept 14.4)

microfilaments and microtubules
groups of lysosomes
groups of ribosomes
groups of chromosomes
groups of peroxisomes

c
Cells are able to distinguish proteins destined for secretion or for segregation to specific intracellular compartments from those that will remain in the cytoplasm because _____. (eText Concept 14.4)

there are two types of ribosomes: one group that synthesizes cytoplasmic proteins only, and another type that synthesizes secreted or compartment-specific proteins only
some proteins, as they begin to be synthesized, contain a signal region that causes the ribosome with its growing polypeptide to attach to the ER and translocate the polypeptide into the lumen (space) of the ER
proteins destined for secretion or for a specific compartment are all synthesized in the nucleus, whereas cytoplasmic proteins are all synthesized in the cytoplasm
each compartment in the cell (the nucleus, lysosome, and so forth) has its own set of ribosomes that synthesize proteins unique to that compartment
ribosomes contain two types of subunits

b
What is the proper order of the following events in the expression of a eukaryotic gene?

1. translation

2. RNA processing

3. transcription

4. modification of protein

(eText Concept 14.4)

1, 2, 3, 4
3, 2, 1, 4
4, 2, 3, 1
2, 3, 4, 1
1, 2, 4, 3

b
The mRNA codons 5(-CAA-3( or 5(-CAG-3( are translated as the amino acid glutamine by _____. (eText Concept 14.4)

the tRNA with an anticodon 5(-GUU-3( and glutamine at its other end
by tRNA molecules that have been charged with glutamine by two different aminoacyl-tRNA synthetases
separate tRNA molecules with anticodons 3(-GUU-5( and 3(-GUC-5(, respectively
the same tRNA with the anticodon 3(-GUU-5(
the small and large ribosomal units

d
Which of the following statements regarding the structure and function of tRNA is false? (eText Concept 14.4)

Each type of tRNA molecule translates a particular mRNA codon into a particular amino acid.
Although each tRNA consists of a relatively short, single RNA strand, this single strand can achieve a three-dimensional structure by folding back upon itself and forming covalent bonds between complementary bases.
The nucleotide sequence at both the amino acid attachment and the anticodon ends of each tRNA is instrumental in specifying which amino acid is attached to the tRNA by aminoacyl-tRNA synthetase.
Although there are 61 codons that code for amino acids, there are only 45 different tRNA molecules.
The second and third listed responses are false.

b
A geneticist found that a particular mutation had no effect on the polypeptide encoded by the gene. This mutation probably involved _____. (eText Concept 14.5)

the deletion of one nucleotide
a missense mutation
the insertion of one nucleotide
a nonsense mutation
a silent or neutral mutation

e
A base-pair substitution mutation in a germ cell line is likely to have no effect on phenotype if the substitution _____. (eText Concept 14.5)

forms a new stop codon
occurs in an intron
changes a stop codon to a codon specifying an amino acid
changes the structure of an enzyme
prevents the initiation of transcription of the DNA sequence that codes for ATP synthase

b
A virus infects a cell and randomly inserts many short segments of DNA containing a stop codon throughout an organism’s chromosomes. This will probably cause _____. (eText Concept 14.5)

manufactured proteins to be short and defective
the DNA to break up into thousands of short segments
incorrect pairing between mRNA codons and amino acids
no bad effects, as long as the stop codons are not also inserted into tRNA
All of the listed responses are correct

a
A point mutation in which a single base pair is inserted or deleted from DNA is called a(n) _____. (eText Concept 14.5)

nonsense mutation
frame-shift mutation
inversion mutation
translocation mutation
missense mutation

b
Ultraviolet (UV) radiation is damaging to cells because it _____. (eText Concept 14.5)

pokes holes in the nuclear envelope
blocks all translation
causes mutations in the DNA
deactivates the enzymes needed for DNA replication
shreds the cytoskeleton and leads to free radicals

c
Transcription factors are found in _____. ()

archaea
bacteria and eukaryotes
bacteria and archaea
eukaryotes
archaea and eukaryotes

e
On the off chance that you might contract an archaeal infection, how might it be treated? ()

It could be treated with antiviral medications because archaea are similar to viruses.
It could be treated with antibiotics such as streptomycin that inactivate bacterial ribosomes because archaea and bacteria have similar ribosomes.
It could be treated with drugs that disrupt gene splicing because archaea remove introns in the nucleus before sending mRNA to ribosomes.
It could be treated with a vaccine.
None of the listed responses is correct.

e
When genes are expressed, they produce _____. ()

enzymes
RNA molecules
phenotypic traits
polypeptides
The second and fourth responses are correct.

e
What is a key difference in gene expression between eukaryotic and prokaryotic cells? ()

In prokaryotes, proteins are assembled directly from DNA.
RNA polymerases are involved only in initiation in eukaryotes.
In prokaryotic cells, the mRNA transcript is immediately available as mRNA without processing.
In eukaryotic cells, transcribed RNA sequences function as termination signals.
Prokaryotes do not contain ribosomes.

c
x

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