Download BioSc 231 Exam 3 2008

BioSc 231
General Genetics
Exam 3
Name __________________________________
Multiple Choice. (2 points each)
1) _____The base Guanine is always paired with ___.
A.
B.
C.
D.
Adenine
Guanine
Cytosine
Thymine
2) _____ Which of the following describes the structure of DNA?
A. A double helix with two parallel strands.
B. A double helix with two anti-parallel strands.
C. A double helix with variable thickness depending on the base paring
3) _____ The role of tRNA is:
A.
B.
C.
D.
E.
to serve as an intermediate in the decoding of genes.
to act as transporters bringing amino acids to the site of protein synthesis.
to serve as general translational components of the ribosome.
to facilitate splicing of pre-messenger RNAs.
to facilitate protein trafficking in protein secretion.
4) _____ ___ is an enzyme that links Okazaki fragments together after the RNA primers have been replaced by DNA.
A.
B.
C.
D.
E.
origin of replication
convertase
primase
ligase
topoisomerase
5) _____ Which of the following is NOT a property of RNA?
A.
B.
C.
D.
E.
It is double stranded
It contains the sugar ribose
Uracil replaces thymine
It is found in the nucleus
All of the above
6) _____ Which of the following constitutes the primary structure of a protein?
A.
B.
C.
D.
E.
The folding of a polypeptide chain.
The linear sequence of amino acids in a polypeptide chain.
The polypeptide chains stacked on top of each other.
A pleated sheet.
Several polypeptide subunits.
7) _____ The chemical bond in a polypeptide by which the carboxyl group of one amino acid is linked to the amino group of the
adjacent amino acid is called a(n) ____ bond.
A.
B.
C.
D.
E.
phosphodiester
peptide
hydrogen
hydrophobic
hydrophilic
8) _____ During the process or translation, as the ribosome moves down the mRNA and exposes the codon for the next amino
acid in the chain, an acylated tRNA with the appropriate anti-codon enters the ___ of the large ribosomal subunit.
A.
B.
C.
D.
A site
P site
E site
S site
9) _____ Which of the following are role(s) of the 5’ cap on eukaryotic mRNA?
A.
B.
C.
D.
The cap helps the RNA polymerase find the promoter and initiate transcription.
The cap plays a role in the removal of introns.
The cap acts as a binding site for the ribosome.
none of the above.
10) _____ The RNA polymerase that produces the primer necessary for DNA synthesis is called the ___.
A.
B.
C.
D.
E.
origin of replication
convertase
primase
ligase
topoisomerase
11) _____ In what cellular compartment are introns removed from pre-mRNA to make mature mRNA?
A.
B.
C.
D.
E.
cytoplasm
nucleus
golgi bodies
mmitochondria
endoplasmic reticulum
12) _____ In prokaryotic organisms, normal self-termination of transcription occurs due to the presence of
A.
B.
C.
D.
stem-loop sequences at the 3’ end of the mRNA
multiple stop codons
multiple RNA polymerase molecules
histones
13) _____ The sigma factor protein’s role in transcription in E. coli includes which of the following?
A.
B.
C.
D.
E.
helps the RNA polymerase to bind to the promoter
contributes to the proofreading activity of RNA polymerase
required for continued extension of the RNA molecule
plays a role in transcription termination
all of the above
14) _____ Which of the following is not a modification of eukaryotic mRNA?
A.
B.
C.
D.
Intron removal
Coupling of transcription and translation
3' polyadenylation
mRNA capping
15) _____ Which of the following is true for histones?
A.
B.
C.
D.
They are rich in acidic amino acids
They are associated with the nucleosome..
They are found in the endoplasmic reticulum.
They form the scaffolding structure.
16) _____ The lac repressor protein controls expression of the lac operon via ______
A.
B.
C.
D.
binding to the lac structural genes to repress expression
binding of the lac Z and lac Y genes only
binding to the lac promoter site to repress expression
binding to the lac operator site to repress expression
Short Answer. (variable points)
17) Griffith did a series of experiments with R and S cells that were injected into mice. What did his experiments show? (2
points)
18) If the GC content of a DNA molecule is 44 percent, what are the percentages of each of the four bases (A,T,C and G)? (2
points)
19) What is the function of transcription factors in eukaryotic transcription (2 points)
20) What is the function of histones? (2 points)
21) A scientist extracted the molecule shown to the right from a bacterial cell.
Did this molecule come from RNA or DNA? Justify your answer (2 points)
Addition of
substrate
)
Enzyme Activity
22) The figure at the right, illustrates expression of
enzyme activity for a catabolic pathway that is
regulated by an inducible repressor system.
On the two lines below, draw the position of
RNAP (
), Repressor (
), and inducer (
(if present) at both t0 and t3. (5 points)
t0
P
O
Z
Y
A
P
O
Z
Y
A
t3
0
1
2
3
Time (hrs)
4
23) The following table contains a list of statements that apply to replication, transcription, both, or neither. In each empty box,
put a check mark if that statement applies to replication or transcription. (8 points)
Replication
Transcription
The new strand is made 5’ to 3’.
The new strand is made 3’ to 5’.
The new strand is identical to the template strand, with the exception of
U’s replacing T’s.
The new strand is complementary to the template strand.
The template strand is RNA.
The product is DNA.
The product is RNA.
An RNA primer is required to initiate synthesis.
Synthesis of the new strand is initiated at a promoter.
24) Below is a segment of a double stranded DNA molecule containing a promoter sequence. Write the sequence of the RNA
molecule that would be produced by the RNA polymerase binding to this promoter (up to the end of the molecule). (5 points)
-35
-10
+1
5’-CGTTCGGATCGATGCCGATCAGCGGGTAGCGGGTGATCTCGGCCGCCGACACCTGCTTGCGGCCGGCCAGCTCGTGGCC–3’
3’-GCAAGCCTAGCTACGGCTAGTCGCCCATCGCCCACTAGAGCCGGCGGCTGTGGACGAACGCCGGCCGGTCGAGCACCGG-5’
25) The following questions refer to the numbers on this figure. (7 points)
(Possible terms are on the next to last page)
A. What end (5' or 3') of the molecule is indicated by arrow number 3?
B. What enzyme functions at the location indicated by number 5 to form phosphodiester bonds between two existing DNA molecules.
C. Is arrow 4 pointing to the template for the leading or lagging strand?
D. What kind of nucleic acid is indicated by arrow number 7?
E. What end (5' or 3') of the molecule is indicated by arrow number 8?
F. What do you call the short DNA fragments indicated by arrow number 6?
G. What enzyme (indicated by arrow 2) unwinds the DNA at the replication fork?
26) Translate the following mRNA using the single letter amino acid code (You can tear off the last page to read the table)
(5 points)
5’ GAGGCCGAUGUACGGCGAGAAUGAAUCAGCGAGGGAGGGCAGAGAAGAGAACUAGGAGCUUUUUUUU 3’
27) Meselson and Stahl used a heavy form of nitrogen to demonstrate semi-conservative DNA replication. Bacterial cells were
grown in the presence of heavy nitrogen until all the DNA contained the heavy form. The bacteria were then transferred to a
medium that only contained the light form of nitrogen. At different time points, DNA was isolated from the bacteria and
subjected to density gradient ultracentrifugation. Some of the following test tube pictures indicate the location of the DNA
band(s) at different points in their experiment. Which tubes represent how the DNA would appear (5 points)
A) At the beginning of the experiment
______
B) After 1 generation
______
C) After 2 generations
______
D) After 10 generations
______
28) The lines and boxes below are a schematic representation of template DNA, mRNA and protein from a prokaryote. Add
labels for the following elements to the boxes or the ends of each molecule (Transcription occurs from left to right in the
diagram) (10 points)
Promoter (-10 and -35)
AUG
Ribosome binding site (RBS)
Transcriptional terminator
5’ and 3’ ends of each nucleic acid molecule.
Amino (N) and carboxyl (C) ends of the resulting protein.
Word List
3’ end
5’ end
Activator
Amino (N) end
Apo-Repressor
AUG
Carboxyl (C) end.
Co-repressor
Coding strand
DNA polymerase I
DNA polymerase III
Helicase
Histones
Lagging strand
Leading strand
Ligase
Nucleosome
Okazaki fragment
Operator
Origin of replication
Polycistronic
Primase
Primer
Promoter
Repressor
Ribosome binding site (RBS)
Scaffolding protein
Single-stranded DNA binding protein
Stop codon
TATA box
Telomerase
Template strand
Topoisomerase
Transcriptional terminator
Upstream activating sequence
Bonus question. (4 pts)
The development of high throughput DNA sequencing techniques were essential for solving the human genome sequence. One of the
important advances was a variation on a method called dideoxy sequencing. Dideoxy sequencing uses dideoxy nucleotides which
include a ribose sugar that lacks both a 2’ and 3’ hydroxyl group. Based on what you know about nucleic acid synthesis, what effect
do you think dideoxy nucleotides have on DNA synthesis?
Bonus question 2. (2 pts)
Translate the following mRNA molecule.
5’GGCGAUGUAUAGCCCUGCCCGCACAGCGAAUAGCUGGAUACUGCUAUGGAUUAACUAGGAGCUUUUUUU 3’
Bonus question 3. (1 pt)
Who is going to win the Michigan State vs. Michigan football game tomorrow?