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ERT 101 Biochemistry
Assignment Nucleic Acid
1. The following is a code for a strand of DNA
DNA
3’ A T A T _
1
2
3
4
5
_ _ T T T
6 7 8
mRNA
9
_
_
_
_
_
_
_
_
10 11 12 13 14 15 16 17 18 19
C
G
U
tRNA
Amino
_
U
U
G
G
M e t
Acid
a) Fill in the blanks to complete the segment of DNA shown.
b) Fill in the blanks to complete the sequence of amino acids coded for the
complementary strand of DNA
c) Write the code for the complementary strand of DNA completed in part a.
d) What would be the effect if C were substituted for T at base 10?
e) What would be the effect if A were substitute for G at base 11?
f) What would be the effect if G were substituted for T at base 14?
g) What would be the effect if C were inserted between base 9 and 10?
G
A
h) How would UV radiation affect this strand of DNA?
i) Identify a nonsense sequence in this strand of DNA.
2. Match the following examples of mutagens.
_____________ A mutagen that is incorporated into DNA in place of a normal base
_____________ A mutagen that causes the formation of highly reactive ions
_____________ A mutagen that alters adenine so that it base-pairs with cytosine
_____________ A mutagen that causes insertions
_____________ A mutagen that causes the formation of pyrimidine dimmers
a. frameshift mutagen
b. nucleoside analog
c. base-pair mutagen
d. ionizing radiation
e. nonionizing radiation
3. Identify three ways of preventing mistakes in DNA.
4. Why are mutation and recombination important in the process of natural selection
and the evolution of organisms?
5. PCR replication of DNA is similar to bacterial population growth. If scientist,
starting PCR with 15DNA helices, runs the reaction for 15 cycles, how many
DNA molecules will be present at the end? Show your calculations.
6. The polymerase chain reaction (PCR) is a technique to produce a large number of
identical molecules of DNA in vitro. Describe in detail the PCR technique.
7. By referring to the Genetic Code,
(i)
What DNA nucleotides triplet codes for codon UGU?
(ii)
Identify a base-pair substitution that would produce a silent mutation at
this codon.
(iii)
Identify a base-pair substitution that would result in a missense mutation
at this codon.
(iv)
Identify a base-pair substitution that would produce a nonsense mutation
at this codon.
8. List and describe the steps in prokaryotic DNA replication. How does this process
appear to differ from eukaryotic DNA?
9. Define and describe the roles of the following in replication.
a. DNA ligase
b. DNA polimerase III
c. primase
d. helicase
e. Okazaki fragments