Unit 3 Review • MHR 325(b)In eukaryotes, mRNA must move to the
cytoplasm before transcription can occur.
(c)Transcription and translation can take place
simultaneously along a single molecule of
mRNA.
(d)Proteins may determine when transcription
takes place.
(e)Proteins may determine when translation
takes place.
9.The characteristics of the genetic code include
(a)redundancy, which means that one codon
can code for several amino acids
(b)universality, which means that the deletion
of a nucleotide triplet will have the same
effect in prokaryotic and eukaryotic cells
(c)continuity, which means that the addition
of a single nucleotide will change the
reading frame for all subsequent codons
(d)a “wobble” in the third nucleotide position,
which creates ambiguity in the code
(e)both redundancy and continuity, which help
to protect the cell against harmful mutations10.Which of the following is not true of promoter
sequences along a stretch of DNA?
(a)They are usually rich in T and A
nucleotides.
(b)They can bind RNA polymerase in more
than one direction.
(c)They can be blocked by polypeptides.
(d)They can be found on both strands of a
DNA molecule.
(e)Their affinity for RNA polymerase can
be changed.
11.Gene expression differs in prokaryotes and
eukaryotes in that
(a)in eukaryotes, mRNA is processed so that
exons are removed
(b)in prokaryotes, only a small portion of the
genome is likely to be expressed during the
life of the cell
(c)in eukaryotes, operons may include genes
on more than one chromosome
(d)in eukaryotes, transcription must be
completed before translation can begin
(e)in prokaryotes alone, many ribosomes can
attach to a single mRNA strand to form a
polyribosome complex
12.Which statement about the lacoperon in E. coli
is not correct?
(a)It is an example of transcriptional
regulation.
(b)An activator can bind directly to the DNA
molecule to promote transcription of the
lacgenes.
(c)A repressor can bind directly to the DNA
molecule to inhibit transcription of the
lacgenes.
(d)Lactose does not bind directly to the DNA
molecule.
(e)The rate of synthesis of the repressor protein
drops when lactose is available to the cell.
13.Some mutations may be silent because
(a)the redundancy of the genetic code means
that a change in the nucleotide sequence of
a gene will not always change the amino
acid sequence of the gene product
(b)they occur in somatic cells rather than
germ cells
(c)they may not affect the transport of the
polypeptide from the cytoplasm to the
target tissue
(d)the continuity of the genetic code means
that a change in the reading frame might
not affect the structure of the final protein
product
(e)cells contain many enzymes that can
correct damage to the DNA molecule
14.A molecule that can enter a cell and cause
random damage to the DNA molecule is known
as a
(a)physical mutagen (d)dimer
(b)chemical mutagen (e)somatic mutagen
(c)base analogue
15.Which of the following statements about
restriction endonucleases is not correct?
(a)They can be used to prepare DNA samples
for fingerprinting.
(b)They can help protect bacteria from
infection by viruses.
(c)They target a specific nucleotide sequence.
(d)They can be used in the polymerase chain
reaction to amplify small amounts of DNA.
(e)They can be used to map sections of DNA
along a chromosome.
16.Stanley Cohen and Herbert Boyer are known
for being the first research team to
(a)sequence a bacterial plasmid
(b)sequence the genome of a virus
(c)clone a mammalian gene in a bacterial vector
(d)create a recombinant bacterial plasmid
(e)use a fluorescent probe to locate a gene on
a chromosome