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818 Chapter 26
Copyright © 2017 Pearson Education, Inc.
Codon:
Anticodon:
GCA
CUU
AGG
CCU
GGU
UCA
GAC
CCU
UUU
AGG
UGA
AAG
GUC
UGC
AAA
ACC
28.
a.
none
none
P A U
Pro-Ala-Leu-Arg
L A B R
b. mRNA
CC(UCA or G)GC(UCA or G)CU(UCA or G)CG(UCA or G)
or
UU(A or G) AG(A or G)
c. DNA (sense strand)
CC(TCA or G)GC(TCA or G)CT(TCA or G)CG(TCA or G)
or
TT(A or G) AG(A or G)
Notice that because mRNA is complementary to the template strand of DNA, which is complementary to
the sense strand, mRNA and the sense strand of DNA have the same sequence of bases (except DNA has a
T where RNA has a U). Also notice that Leu and Arg are each specified by six codons.
29.
a.
CC and GG
c.
CA and TG
CA and TG are formed in equal amounts because A pairs with T and C pairs with G.
C
G
A
T
5'
3'
3'
5'
(Remember that the dinucleotides are written in the 5
S
3 direction. For example, part
f
is not a correct
answer because it has A pairing with A and T pairing with T.)
30.
AZT is incorporated into DNA when the 3 -OH group of the last nucleotide incorporated into the grow-
ing chain of DNA attacks the
a
-phosphorus of AZT-triphosphate instead of the
a
-phosphorus of a normal
nucleotide. When AZT is thus incorporated into DNA, DNA synthesis stops because AZT does not have a
3 -OH group that can react with another nucleotide.
31.
UUU
=
phenylalanine
UUG
=
leucine
GGU
=
glycine
GGG
=
glycine
UGU
=
cysteine
GUG
=
valine
GUU
=
valine
UGG
=
tryptophan
32.
The number of different codons using four nucleotides:
for a two-letter code: (4)
2
=
16
for a three-letter code: (4)
3
=
64
for a four-letter code: (4)
4
=
256
27.