Micro 302 Second Exam, March, 2002
Multiple Choice Questions (2 points each)
Circle the letter next to the single best answer
1. When genes are regulated by steroid hormones, the steroid binds to:
a) snRNP particles in the nucleus and this promotes splicing of messenger RNA
b) Primary transcript RNA and promotes alternative splicing
c) Receptor proteins in the cytoplasm which then move into the nucleus
d) Receptor proteins in the cell membrane that pass the signal on to other proteins in the nucleus
e) A nuclear protein that binds to the CCAAT box that is found in the promoter region of some genes
2. Compared to typical bacteria such as E. coli, mammals such as mice and men have approximately:
a) 5 times as many genes and 100 times as much DNA
b) 10 times as many genes and 30 times as much DNA
c) 20 times as many genes and 100 times as much DNA
d) 10 times as many genes and 1000 times as much DNA
e) 30 times as many genes and 1000 times as much DNA
3. Which of the following statements is FALSE?
a) The nucleus of eukaryotic cells contains several chromosomes
b) Eukaryotic chromosomes are linear and have two centromeres
c) Eukaryotic cells are larger than prokaryotic ones and only eukaryotes possess membrane bound organelles
d) Eukaryotic chromosomes contain a large percentage of non-coding DNA
e) Eukaryotic messenger RNA is monocistronic
4. Which of the following statements is true for the promoters of eukaryotic genes that use RNA polymerase II?
a) The initiator box is downstream of both the AUG start codon and the TATA box
b) The TATA box is downstream of the upstream elements and upstream of the initiator box
c) The upstream elements are upstream of the promoter but downstream of the transcriptional start site
d) The TATA box is upstream of the transcriptional start site but downstream of the initiator box
e) The initiator box is upstream of the first exon and downstream of the translational start site
5. During the packaging of DNA in the eukaryotic cell nucleus:
a) DNA is wound around nucleosomes by DNA gyrase
b) Histones are negatively charged proteins that bind to DNA
c) Each nucleosome contains approximately 200 histones
d) The nucleosome core particle contains 8 histone proteins
e) Histones are arranged helically around the DNA forming 30 nm fibers
6. The Cap and Tail of eukaryotic messenger RNA consist of the following:
a) The Cap consists of the sequence AAAUAA added at the 5'-end
b) The Cap contains a single guanine nucleotide and the tail contains many methylated adenosine nucleotides
c) The Cap contains a single methylated guanine nucleotide and the tail contains many adenosine nucleotides
d) The Tail consists of a long sequence of A's added at the 5'-end
e) The Cap consists of a single guanine nucleotide added at the 3'-end
7. Regulatory sequences known as enhancers:
a) Are needed for transcription by RNA polymerase III but not by RNA polymerase II
b) Encode the snRNA molecules needed for splicing RNA
c) May be located upstream or downstream of the promoter
d) Are where RNA polymerase first binds when it transcribes a gene
e) Consist of short repeated sequences of 6, 8 or 10 bases
8. When the sequences of their ribosomal RNA are compared:
a) Chloroplasts are most closely related to archaea (archaebacteria)
b) Mitochondria are most closely related to the animal cell nucleus
c) Chloroplasts are most closely related to the fungal cell nucleus
d) Mitochondria are most closely related to the plant cell nucleus
e) Chloroplasts are most closely related to bacteria
9. During the formation of protozoan mRNA by self-splicing, the role of the internal guide sequence (IGS) is as follows:
a) the IGS recognizes the 5' splice site instead of U1
b) the IGS recognizes the 3' splice site instead of U5
c) the IGS recognizes the branch site instead of U3
d) the IGS recognizes the small subunit ribosomal RNA
e) the IGS recognizes the tail recognition site
10. The difference between a true revertant and a second site revertant is that:
a) A true revertant has the original DNA sequence restored
b) A true revertant has an altered protein, but this works as well as the original version
c) A second site revertant had two original mutations, both of which have reverted
d) A second site revertant results from an insertion followed by a deletion (or vice versa) so that the overall length of the DNA is unchanged
e) A true revertant relies on having a gene duplication to replace the defective copy
11. Which of the following does NOT cause a frameshift?
a) Insertion of one base into a coding region
b) Deletion of five bases from a coding region
c) Insertion of three bases into a coding region
d) Deletion of two bases from a coding region
e) Insertion of three bases into a regulatory region
12. A base analog is a chemical that:
a) Converts one base to another by altering amino groups to hydroxy groups
b) Hydrolyses pyrimidine bases off from the deoxyribose to which they were attached
c) Distorts a DNA double helix by binding to base pairs
d) Is mistakenly incorporated into DNA by DNA polymerase
e) Absorbs ultraviolet radiation and reacts with DNA
13. Eukaryotic ribosomes differ from prokaryotic ribosomes in the way they translate mRNA as follows:
a) In prokaryotes the start codon is always the first AUG
b) In eukaryotes mRNA first binds to the large subunit of the ribosome
c) In eukaryotes the mRNA binds to ribosomal RNA by its tail recognition sequence
d) In prokaryotes the initiator tRNA binds to the Shine Dalgarno sequence
e) In eukaryotes the mRNA is bound by Cap binding protein before it binds to the ribosome
14. The Ames test for detecting mutations relies on:
a) Producing mutants of bacteria that are resistant to mutagens
b) Reversion of mutant bacteria that cannot make histidine
c) The fact that all common mutagens cause the same type of defects at the molecular level
d) The splitting of thymine dimes by ultraviolet radiation
e) The fact that bacteria only have a single chromosome and no nucleus
15. The following events usually result in a silent mutation EXCEPT:
a) a mutation that occurs in a non-coding region
b) a mutation that occurs in an intergenic region
c) a mutation that changes the third base of a codon but the codon still codes for the same amino acid
d) a mutation that occurs in the splice site of an intron
e) a mutation that occurs in the central region of an intron
16. A radical replacement is a base substitution that results in:
a) an exon being substituted with an intron during a splicing event
b) a codon coding for an amino acid being substituted with a stop codon
c) one amino acid being replaced with another amino acid with similar chemical properties
d) one amino acid being replaced with another amino acid with very different chemical properties
e) a change in the promoter
Short Answer Questions (points are indicated for each question)
17. (12 pts) Use the following items to answer the next six questions:
A) Transcriptional regulation
B) Translational regulation
C) Post-translational regulation
____ The effect of lactose on the lac repressor (LacI) is an example of this
____ Antisense RNA functions at this level
____ The rapid degradation of certain mRNAs is an example of this
____ The effect of the CRP-cAMP complex on a suite of different genes is an example of this
____ The effect of the LacI repressor on the lac operon is an example of this
____ The targeted degradation of specific proteins is an example of this
18. (FOUR points) Define or explain any TWO of the following terms briefly: a) snRNA; b) primary transcript; c) lariat structure; d) alternative splicing
19. (FOUR points) Define or explain any TWO of the following types of mutations briefly: a) translocation; b) inversion; c) nonsense mutation; d) temperature sensitive mutation
20. (3 pts) Name three of the four types of proteins discussed in class.
1) ___________ 2) ___________ 3) ___________
21. (2 pts) Give the full name of the protein encoded by the lacZ gene.
22. (3 pts) (Circle the correct answers) A catabolic pathway is often regulated by the amount of substrate/product whereas an anabolic pathway is usually regulated by the amount of substrate/product. The lac operon is an example of genes that encode a catabolic/anabolic pathway.
23. (4 pts) DRAW the process of repression. On your graphic, label the following items: promoter, operator, repressor protein, and RNA polymerase (RNAP).
24. (3 pts) Using the following letter codes, put the steps of translation elongation in order:
A) Peptidyl transfer (peptide bond formation)
B) Entry of incoming charged tRNA
C) Translocation
_____ >> _____ >> _____
25. (2 pts) (Circle the correct answers) Immediately before translocation, the empty tRNA is located in the A/E/P site of the ribosome whereas immediately following translocation, the empty tRNA is located in the A/E/P site of the ribosome.
26. (6 pts) DRAW a graphic depicting the initiation complex for translation. On your drawing, label the following: 30S subunit, 50S subunit, A site, E site, P site, initiator tRNA, and mRNA with start codon.
27. (4 pts) In two COMPLETE sentences or less, explain the advantages and disadvantages to the cell of both transcriptional regulation and post-translational regulation.
28. (10 pts) Use the following choices to answer the next set of questions:
A) Transformation, B) Transduction, C) Conjugation, D) All of the above, E) None of the above
_____ Is mediated by phage.
_____ Is mediated by the F plasmid.
_____ Requires cell-to-cell contact
_____ Transfer of the genetic material is unidirectional
_____ The donor cell MUST be alive
29. (3 pts) On the following graphic (graphic = a picture of a gel with two bands and the positive and negative electrodes shown).
* indicate which band represents a DNA fragment of 2 kb in size
* indicate which band represents a DNA fragments of 6 kb in size
* draw an arrow indicating the direction of DNA migration through the gel
30. (2 pts) Define a replicon (in one complete sentence).
31. (3 pts) Match the following components of a plasmid cloning vector to their purpose during cloning. You will not use all of the items.
A) bla gene B) oriT C) oriV D) MCS E) lacZ gene
_____ Used for blue/white color selection
_____ Used as a marker gene for antibiotic resistance
_____ Used as the site of DNA insertion
32. (3 pts) Name three of the five components discussed in class that a YAC (yeast artificial chromosome) must have.
1) ___________ 2) ___________ 3) ___________