Genetics Exam 3 Moehnke Questions With Complete
Solutions
A geneticist isolates a gene for a specific trait under study. She
also isolates the corresponding mRNA. Upon comparison the
mRNA is found to contain 1,000 fewer bases than the DNA
sequence. Did the geneticist isolate the wrong DNA?
a. Yes, mRNA is made from a DNA template and should be the
same length as the gene sequence
b. Yes, the mRNA should contain more bases than the DNA
sequence because bases flanking the gene are also transcribed
c. No, the final mRNA contains only exons, the introns were
removed
d. No, the mRNA was partially degraded after it was transcribed
Correct Answers No, the final mRNA contains only exons the
introns were removed
A lac operon of genotype lacI+ lacP+ lacO+ lacZ+ lacY- will
produce B-galactosidase but NOT perm ease when
a. in the presence OR absence of lactose
b. lactose is present
c. lactose is absent
d. glucose is present Correct Answers lactose is present
A mutant bacterial cell has a defective aminoacyl synthetase that
attaches a lysine to tRNAs with the anticodon AAA instead of a
phenylalanine. The consequence of this for the cell will be that
a. none of the proteins in the cell will contain phenylalanine
b. proteins in the cell will include lysine instead of
phenylalanine at amino acid positions specified by the codon
UUU
,c. cell will compensate for the defect by attaching phenylalanine
to tRNAs with lysine specifying anticodons
d. the ribosome will skip a codon every time UUU is
encountered Correct Answers proteins in the cell will include
lysine instead of phenylalanine at amino acid positions specified
by the codon UUU
A mutation in the 5' UTR of the trp operon results in region 2
always pairing with region 3. Which of the following would be
the result of this particular mutation on the trp operon when high
level of tryptophan is available in the cell?
a. Transcription would be no longer repressible
b. Attenuation would no longer occur
c. The mutation does not affect the trp operon at all
d. Transcription would be immediately initiated Correct
Answers Attenuation would no longer occur
A mutation in which of the following parts of a gene is likely to
be most damaging to a cell?
a. intron
b. exon
c. 5' UTR
d. 3' UTR
e. All would equally damaging Correct Answers exon
A mutation that prevents that catabolite activator protein (CAP)
from binding to the lac operon promoter will result in
a. no change in the operon
b. an increase in the transcription of the lac structural genes
c. a decrease in the ability of RNA polymerase to bind the
promoter
,d. an increase in the ability for RNA polymerase to bind to the
promoter Correct Answers a decrease in the ability of RNA
polymerase to bind the promoter
A particular triplet of bases in the template strand of DNA is 5'
AGT 3'. The corresponding codon for the mRNA transcribed is
a. 3' UCA 5'
b. 3' UGA 5'
c. 5' TCA 3'
d. 3' ACU 5' Correct Answers 3' UCA 5'
A person born with an inherited predisposition to cancer usually
does not develop cancer until after
a. exposure to radiation
b. LOH of inherited mutation
c. age 70
d. Mardis Gras Correct Answers LOH of inherited mutation
A substitution from a purine to a pyrimidine or a pyrimidine to a
purine is known as a
a. transversion mutation
b. inversion mutation
d. translocation mutation
c. transition mutation Correct Answers transversion mutation
All of the following statements about replication origins are true
except:
a. A bacterial chromosome has one origin of replication
b. A eukaryotic chromosome has one origin of replication
c. Replication origins are unique DNA segments that contain
multiple short repeated sequences
, d. Replication origins usually contain an AT-rich stretch
Correct Answers A eukaryotic chromosome has one origin of
replication
All of the following statements about Typer I topoisomerase
(Topo I) are true except:
a. Topo I removes DNA supercoils in an ATP-dependent
reaction
b. Topo I from eukaryotic cells can remove both positive and
negative supercoils
c. Topo I from E. coli can remove only negative supercoils
d. Topo I is essential for viability in E. coli Correct Answers
Topo I removes DNA supercoils in an ATP-dependent reaction
Alternative RNA splicing
a. is a mechanism for increasing the rate of transcription
b. can allow the production of proteins of different sizes from a
single mRNA
c. can allow the production of similar proteins from different
RNAs
d. increases the rate of transcription Correct Answers can
allow the production of proteins of different sizes from a single
mRNA
An antibiotic interferes with the ability of the ribosome to move
down mRNA. Which of the following is this chemical most
likely affecting?
a. EF-Tu
b. EF-Ts
c. EF-G
d. IF2 Correct Answers EF-G
Solutions
A geneticist isolates a gene for a specific trait under study. She
also isolates the corresponding mRNA. Upon comparison the
mRNA is found to contain 1,000 fewer bases than the DNA
sequence. Did the geneticist isolate the wrong DNA?
a. Yes, mRNA is made from a DNA template and should be the
same length as the gene sequence
b. Yes, the mRNA should contain more bases than the DNA
sequence because bases flanking the gene are also transcribed
c. No, the final mRNA contains only exons, the introns were
removed
d. No, the mRNA was partially degraded after it was transcribed
Correct Answers No, the final mRNA contains only exons the
introns were removed
A lac operon of genotype lacI+ lacP+ lacO+ lacZ+ lacY- will
produce B-galactosidase but NOT perm ease when
a. in the presence OR absence of lactose
b. lactose is present
c. lactose is absent
d. glucose is present Correct Answers lactose is present
A mutant bacterial cell has a defective aminoacyl synthetase that
attaches a lysine to tRNAs with the anticodon AAA instead of a
phenylalanine. The consequence of this for the cell will be that
a. none of the proteins in the cell will contain phenylalanine
b. proteins in the cell will include lysine instead of
phenylalanine at amino acid positions specified by the codon
UUU
,c. cell will compensate for the defect by attaching phenylalanine
to tRNAs with lysine specifying anticodons
d. the ribosome will skip a codon every time UUU is
encountered Correct Answers proteins in the cell will include
lysine instead of phenylalanine at amino acid positions specified
by the codon UUU
A mutation in the 5' UTR of the trp operon results in region 2
always pairing with region 3. Which of the following would be
the result of this particular mutation on the trp operon when high
level of tryptophan is available in the cell?
a. Transcription would be no longer repressible
b. Attenuation would no longer occur
c. The mutation does not affect the trp operon at all
d. Transcription would be immediately initiated Correct
Answers Attenuation would no longer occur
A mutation in which of the following parts of a gene is likely to
be most damaging to a cell?
a. intron
b. exon
c. 5' UTR
d. 3' UTR
e. All would equally damaging Correct Answers exon
A mutation that prevents that catabolite activator protein (CAP)
from binding to the lac operon promoter will result in
a. no change in the operon
b. an increase in the transcription of the lac structural genes
c. a decrease in the ability of RNA polymerase to bind the
promoter
,d. an increase in the ability for RNA polymerase to bind to the
promoter Correct Answers a decrease in the ability of RNA
polymerase to bind the promoter
A particular triplet of bases in the template strand of DNA is 5'
AGT 3'. The corresponding codon for the mRNA transcribed is
a. 3' UCA 5'
b. 3' UGA 5'
c. 5' TCA 3'
d. 3' ACU 5' Correct Answers 3' UCA 5'
A person born with an inherited predisposition to cancer usually
does not develop cancer until after
a. exposure to radiation
b. LOH of inherited mutation
c. age 70
d. Mardis Gras Correct Answers LOH of inherited mutation
A substitution from a purine to a pyrimidine or a pyrimidine to a
purine is known as a
a. transversion mutation
b. inversion mutation
d. translocation mutation
c. transition mutation Correct Answers transversion mutation
All of the following statements about replication origins are true
except:
a. A bacterial chromosome has one origin of replication
b. A eukaryotic chromosome has one origin of replication
c. Replication origins are unique DNA segments that contain
multiple short repeated sequences
, d. Replication origins usually contain an AT-rich stretch
Correct Answers A eukaryotic chromosome has one origin of
replication
All of the following statements about Typer I topoisomerase
(Topo I) are true except:
a. Topo I removes DNA supercoils in an ATP-dependent
reaction
b. Topo I from eukaryotic cells can remove both positive and
negative supercoils
c. Topo I from E. coli can remove only negative supercoils
d. Topo I is essential for viability in E. coli Correct Answers
Topo I removes DNA supercoils in an ATP-dependent reaction
Alternative RNA splicing
a. is a mechanism for increasing the rate of transcription
b. can allow the production of proteins of different sizes from a
single mRNA
c. can allow the production of similar proteins from different
RNAs
d. increases the rate of transcription Correct Answers can
allow the production of proteins of different sizes from a single
mRNA
An antibiotic interferes with the ability of the ribosome to move
down mRNA. Which of the following is this chemical most
likely affecting?
a. EF-Tu
b. EF-Ts
c. EF-G
d. IF2 Correct Answers EF-G
