Biology 122, Quiz 7, 2012
Name: ______________________________
Directions: 1) Print your name LEGIBLY on BOTH the scantron form and this question sheet; 2) Fill
in the scantron form appropriately – don’t mark on this question sheet; Turn both the scantron form
and this answer sheet in.
1. The location of protein synthesis in eukaryotic cells is the
A. nucleus.
B. cytoplasm.
C. plasma membrane.
D. Golgi apparatus.
E. vacuole
2. In eukaryotes, mRNA processing involves all of the following events except
A. elongation of the transcript.
B. addition of a 5' cap.
C. addition of a poly A to the 3' end.
D. pre-mRNA splicing.
E. association with the spliceosome.
3. Cells can conserve energy and resources by making proteins only when they are needed. Which of the
following levels of control is the most energy-efficient?
A. transcription regulation
B. degrade the mRNA after it is made
C. prevent translation of the mRNA at the ribosome
D. degrade the protein after it is made
4. Which of the following is required for formation of the transcription initiation complex for protein
coding genes in eukaryotes?
A. binding of a transcription factor to the TATA box, recruitment of additional transcription factors,
and recruitment of RNA polymerase II
B. binding of a transcription factor to the operon, recruitment of additional transcription factors, and
recruitment of RNA polymerase III
C. binding of a single transcription factor to the TATA box and recruitment of RNA polymerase II
D. binding of RNA polymerase II to the TATA box and core promoter
The following should be well known to you, but just in case, use the following in answering questions 5-8.
The Lac- phenotype (lac minus) is characterized by an absence of lactose operon gene products (proteins)
whether or not lactose is present. The Lacc phenotype (lac constitutive) is characterized by the presence of
lactose operon gene products (proteins) whether or not lactose is present. The Lac + phenotype (wild-type)
characterized by the presence of lactose operon gene products (proteins) if lactose is present and the
absence of lactose operon gene products (proteins) if lactose is absent. All of the above assumes that
glucose is not present.
5. A mutation is recovered that maps to the LacI repressor gene. This mutation causes an inability of the
repressor protein to bind lactose. Bacteria that have this mutation would likely exhibit which of the
following phenotypes?
A. LacB. Lacc
C. Lac+
D. none of the above
6. A mutation is recovered that maps to the LacI repressor gene. This mutation causes an inability of the
repressor protein to bind DNA. Bacteria that have this mutation would likely exhibit which of the following
phenotypes?
A. LacB. Lacc
C. Lac+
D. none of the above
7. A mutation is recovered that maps to the Operator region of the lactose operon. This mutation is a
change in the nucleotide sequence of the Operator. Bacteria that have this mutation would likely exhibit
which of the following phenotypes?
A. LacB. Lacc
C. Lac+
D. none of the above
8. A mutation is discovered in the gene that encodes the tryptophan operon repressor. This mutation renders
the trp repressor incapable of binding the amino acid tryptophan. Which of the following phenotypes would
result?
A.
a trp minus phenotype (no transcription of the operon, independent of tryptophan levels)
B.
overexpression of one of the genes of the operon, but not the others
C.
no expression of the trpB gene, but normal expression of the other genes in the operon.
D.
a trp constitutive phenotype (transcription of the operon, independent of
Tryptophan levels).
E.
normal expression of the operon.
9. Which of the following is NOT a DIFFERENCE between prokaryotic and eukaryotic gene regulation?
A. translation of eukaryotic mRNA into protein is not coupled to transcription of the mRNA from DNA,
but in prokaryotes it is so coupled
B. prokaryotic mRNA is NOT capped by a 5’mG after transcription, but eukaryotic mRNA is so capped
C. prokaryotic translation and eukaryotic translation use different genetic codes to translate mRNA
codons into amino acid sequences of proteins
D. eukaryotic mRNAs are monocistronic (encode single proteins), whereas prokaryotic mRNAs are
polycistronic (encode multiple proteins)
E. prokaryotic mRNA is not modified by polyadenylation after transcription, but eukaryotic mRNA is so
modified.
10. As you know, merodiploids can be produced that have 2 copies of a given bacterial operon. In the
following merodiploid genotype, what would likely be the lac operon phenotype, remembering that lacZ
encodes one of the gene products (proteins) of the operon?
LacI+ O+ Z__________
LacIc O+ Z+
A. LacB. Lacc
C. Lac+
D. none of the above