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Section 2: Free-Response Question HO
– O P O
Write your answer to each part clearly. Support your answers N N N N N H
with relevant information and examples. Where calculations O O O O O O H H N OH
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N
N
are required, show your work. CH 2 2 2 N N N N N N N N G N H N N O O O N N N N N
N H
A researcher was successful in performing a DNA H O O O CH 2
O
extraction. A short sequence of this DNA was isolated – O O P O – O P O
O
O
for further study. The figure shows the basic structure of O N N N N N H N H O O O CH O O
CH
DNA with four pairs of nucleotides. O O O N N N A N H N N 3
N
N
CH 2 2 2
N N N N N O O O N N N N N
(a) Identify the location of the 3´ and 5´ ends of each strand O O O CH 2
of DNA and describe why you chose those places. O O
O
O
– O P O – O P P O
(b) Write out the order of the bases of the unlabeled DNA O H C C O O O H N N H N N N O

3

5
strand with ′ → ′ 3 directionality. Briefly describe CH 2 2 2 O O O T N N H N N N N N N
why you chose these bases. N N N O O O N N N N N
O O O CH 2
(c) Describe the process by which this DNA strand could O O
O
O
be lengthened. – O P O H – O P O
O N H O O N N N N N O
(d) Describe how the figure would look different if it CH 2 2 2 O O O C N N N H N N N N
N
N
were RNA instead of DNA. N N N O O H N N N N N N
H O O O CH 2
(e) Explain the process and bonds involved in the abil- OH O
O
O
ity of RNA to fold into complex three- dimensional – O P O
OH
shapes, similar to those of tertiary proteins.

MODULE 5 Nucleic Acids 87

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