Name: _________________________________
Genetics 314 - Spring 2006
Exam 1 – 100 points
1. You can characterize the composition of DNA just be heating and cooling it in a
controlled manner.
a) What information about the composition of DNA can you gain by denaturing
(heating) it? Briefly explain your answer.
b) What information can you gain by slowly renaturing (cooling) the DNA?
c) Draw Cot curves for a virus, prokaryotic organism and a eukaryotic organism
labeling features of the three curves that allow you to differentiate the types of
organisms based on the behavior of their respective DNA as it is cooled and
renatures.
2. In what manner does DNA replicate? Briefly explain your answer and diagram what
you would expect to see after two replications of DNA using solid lines to indicate
the original DNA strands and dashed lines for any replicated strands.
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Name: _________________________________
3. You are given the following strand of DNA that codes for a simple polypeptide.
3’ TAC CCC TCG ACG CCG TTT GGG AAA AGC ACC CGA ATT 5’
a) What would be the sequence of the complimentary DNA strand for given DNA
sequence? For full credit label the 3’ and 5’ ends of the complimentary DNA
stand.
b) Using the original DNA sequence as a template, What would be the mRNA
sequence coded for by this strand of DNA? For full credit label the 3’ and 5 ‘
ends of the mRNA strand.
c) Using the codon table at the end of the exam, give the amino acid sequence coded
for by the mRNA strand in your answer to ‘b’.
d) While none of the codons in your mRNA repeat, some of the amino acids occur
more than once. Why is that possible and how could such a system be
advantageous to an organism during translation?
4. To get a DNA sequence transcribed and translated in a prokaryotic organism what
other DNA sequences would you need to add and what would be their functions?
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Name: _________________________________
5. In developing transgenic plants there is great concern that the artificial genes will get
into other organisms with disastrous results.
a) If you are creating a gene to go into an eukaryotic organism, how can you insure
that the gene would produce a non-functional protein product if the gene was
accidentally taken in by a prokaryotic organism? Briefly explain your answer.
b) In some cases you would want to isolate a gene from a eukaryotic organism and
have the gene expressed correctly in a prokaryotic organism. What would you
need to base your DNA sequence on to insure the prokaryote could correctly
transcribe and translate your gene? Briefly explain your answer.
6. You decide to reproduce your gene without any organism, using an in vitro DNA
replication kit you find on the shelf in the lab. The box is open but it appears
everything need to replicate DNA is in the kit. Your piece of DNA is in circular form
and the kit says it mimics prokaryotic replication.
a) You run your reaction and find that you do not recover any replicated DNA.
Using an electron microscope you determine that the DNA is opening but no new
DNA is being synthesized. You add DNA polymerase III and the reaction still
does not occur. What is wrong and how would you fix it to get replication?
b) A friend is also having trouble replication DNA with a kit he bought. He thinks
the reason he is not getting complete replication is that he is missing telomerase.
Before agreeing you ask if the DNA is circular or linear. Why?
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Name: _________________________________
7. Now that you have replicated your circular DNA you decide to use an in vitro
transcription to transcribe your gene. Instead of using a kit you decide to buy the
enzymes ala carte (individually) to save money. You find a source of RNA
polymerase on line that claims it contains everything for successful transcription of
prokaryotic genes.
a) You add your DNA to the RNA polymerase solution and get variable sized pieces
of RNA produced. What could cause variable lengths of transcripts to be
produced and how could your fix the problem.
b) You call the company to tell them they forgot to add something and they
apologize and explain that there had been a packaging error and that the kit sent
was meant for eukaryotic gene transcription. Could this explain why you were
missing something from your RNA polymerase solution and you got variable
sized pieces of RNA produced? Briefly explain your answer.
8. You now have the transcripts you need to produce your protein product by in vitro
translation. You find several kits on-line that make some interesting claims.
a) The first company says while it charges a little more for its kit it is worth it
because it claims that even if the transcripts produced are longer than they should
be, as long as the transcript has the correct leader sequence and a start codon they
guarantee the correct protein product. Is this guarantee worth it or should you
refuse to pay extra for the kit? Briefly explain your answer.
b) A second company claims its kit is better because it saves you money by only
having 43 tRNAs in the kit instead of 61 tRNAs and still produce a protein
product. Can their claims be true? What conditions would you need addressed
before accepting their claim?
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Name: _________________________________
9. You have a bacterial infection and the health center gives you an antibiotic that
targets translation, specifically binding of the small subunit of the ribosome to the
mRNA.
a) How would this affect the bacteria’s ability to produce proteins by translation?
b) Why would this not also affect translation in your cells?
Extra Credit
DNA replication for small pieces of DNA is now done routinely using the polymerase
chain reaction (PCR) where only TAQ DNA polymerase, nucleotides, magnesium DNA
primers and double stranded DNA are placed in the reaction. How is it possible to
replicate DNA with these few ingredients? Also, what enzymes/proteins are being
replaced and what is replacing them to allow DNA replication?.
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Name: _________________________________
RNA Codons
UUU
UUC
UUA
UUG
phe
phe
leu
leu
UCU
UCC
UCA
UCG
ser
ser
ser
ser
UAU
UAC
UAA
UAG
tyr
tyr
stop
stop
UGU cys
UGC cys
UGA stop
UGG trp
CUU
CUC
CUA
CUG
leu
leu
leu
leu
CCU
CCC
CCA
CCG
pro
pro
pro
pro
CAU
CAC
CAA
CAG
his
his
gln
gln
CGU
CGC
CGA
CGG
arg
arg
arg
arg
AUU
AUC
AUA
AUG
ile
ile
ile
met
ACU
ACC
ACA
ACG
thr
thr
thr
thr
AAU
AAC
AAA
AAG
asn
asn
lys
lys
AGU
AGC
AGA
AGG
ser
ser
arg
arg
GUU
GUC
GUA
GUG
val
val
val
val
GCU
GCC
GCA
GCG
ala
ala
ala
ala
GAU
GAC
GAA
GAG
asp
asp
glu
glu
GGU
GGC
GGA
GGG
gly
gly
gly
gly
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