Chemistry 160 Exam 5 key
Please put your name on this exam. Be sure to answer all of the questions as completely as
possible. There is some useful information attached.
100 points
(5) 1. Give three differences between DNA and RNA.
DNA has T, RNA has U; DNA has 2 deoxyribose while RNA has ribose; DNA double stranded, RNA is
single.
(5) 2. Give 2 other examples of molecules (other than DNA or RNA) that contain nucleotides and the
nucleotides they contain.
NAD, FAD , Coenzyme A all have adenine
(5) 3. When we say that DNA is “self complementary” what does that mean?
One strand is complementary to the other
(5) 4. Draw a G-C base pair.
H
N
O -- -- -- H
N
NH -- -- --
N
N
N
N
O
N H -- -- -H
Guanine
cytosine
(5) 5. What are histones?
Positively charged proteins that bind to DNA that allow it to roll up
(5) 6. Describe the structure of DNA.
Double helix with antiparallel strands. Made from a backbone of sugar-phosphate repeating units with
the sugar being 2-deoxyribose. The phosphates form a phosphodiester linkage between the 3’ carbon
of one sugar and the 5’ of the other.
(10) 7. Draw a single strand of DNA with the sequence G – A - T – C
O
5' end
N
N
O
O
P
O
G
CH2
N
O
N
NH2
O
NH2
O O
O
N
N
P
O
CH2
N
O
A
N
O
O
O
N
O P
O
CH2
N
O
T
O
NH2
O
O
N
O P
O
CH2
C
O
N
O
OH
3 ' end
(10) 8. Describe the Sanger dideoxy method for DNA sequencing. What is the importance of the dideoxy
nucleotides in this process.
4 samples of the DNA are put into separate test tubes. Each test tube contains the necessary
substances to make a new piece of dna. ..all of the enzymes, all of the nucleotides etc. However each
test tube contains a dideoxy nucleotide as well. This will cause chain termination when it is inserted.
That means, for example, that if there is dideoxy T, we will get strands ending in T. Each test tube, then
gets its contents run on a gel that can resolve single nucleotide differences. The gel is read from the
bottom up.
(5) 9. Give the central dogma of information transfer.
DNA -- DNA = replication
DNA--------- RNA ------ protein
Transcription translation
(5) 10. How is the vectorial nature of macromolecules maintained through information transfer?
5’ end of the RNA codes for the amino terminus of the protein
(5) 11. For transcription, how does RNA polymerase know where to start?
Upstream promoter sequence
(5) 12. What are introns and exons? What type of information is contained in each?
Introns are intervening sequences of rna that are excised and never translated. Exons are translated.
(10) 13. Describe, using a diagram the process of translation.
See next page for diagram. However, RNA binds to ribosomes . two pieces of tRNA bind to the
ribosome bringing in their amino acids. The amino acids bind and the ribosome shifts over kicking out
the tRNA on the 5’ end. Then the process repeats until a stop codon is found.
Use the DNA sequence below to answer questions 14 and 15
1
5
10
15
20
25
30
35
40
3’ DNA G C A A T C T A C C A G C T C T C C T G T T A A T C G C G C A A C A C T A G C C T
5’ RNA C G U UAGA U G G U C G A GAGGA C AA U U AG C G C G U UG U GA U C G G A
5’
(10) 14. a. Determine the RNA sequence.
SEE ABOVE
b. Using the Genetic code, determine the amino acid sequence.
VERTISAL
(10) 15. For each of the mutations listed below, give the new amino acid sequence and indicate if it
would have a significant effect on the function of the protein.
a. Nucleotide 2 is changed to a G.
no change
b. Nucleotide 15 is changed from a C to a T.
VDRTISAL
c. Nucleotide 27 is changed from a G to a T.
vertical
d. Nucleotide 20 is deleted.
VERRTLGRCDR
e. A Guanine (G) is inserted after nucleotide 39.
No change
Useful Information
O
N
N
H
N
NH
N
H
NH2
N
Guanine
NH
N
N
H
N
Adenine
N
H
OH
H
OH
H
OH
H
OH
CH2OH
CH2OH
Uracil
cytosine
H
H
O
N
H
O
OH
NH
N
O
Thymine
O
O
NH2
O
NH2
ribose
2 - deoxyribose
Genetic Code
U
First
letter
U
F
F
L
L
L
second letter
C
A
S
Y
S
Y
S
Stop
S
Stop
P
H
G
C
C
Stop
W
R
L
P
H
R
L
P
Q
R
L
I
I
I
M, start
V
V
V
V
P
T
T
T
T
A
A
A
A
Q
N
N
K
K
D
D
E
E
R
S
S
R
R
G
G
G
G
C
A
G
U
C
A
G
U
C
A
G
U
C
A
G
U
C
A
G
Third
letter
O