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Module 5 summary
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PREP FOR THE AP EXAM • DNA strands have polarity, with a 5′-phosphate group
REVISIT THE BIG IDEAS at one end and a 3′-hydroxyl group at the other end.
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INFORMATION STORAGE AND TRANSMISSION: describe

the properties of nucleotides and nucleic acids that allow • Nucleotide triphosphates react with a strand of DNA to
them to store genetic information and to pass it accurately make the polymer one nucleotide longer. In the process,
from cell to cell and parent to offspring. the phosphodiester bond of the DNA backbone is
formed. Page 80
LG 5.1 Nucleotides are the building blocks of • Genetic information is stored in the sequence, or order,

nucleic acids. of the nucleotides in nucleic acids. Page 81

• Nucleotides assemble to form nucleic acids, which store

and transmit genetic information. Page 78 LG 5.3 Cellular DNA takes the form of a double
• Nucleotides are composed of a nitrogen-containing base, helix.

a 5-carbon sugar, and a phosphate group. Page 78 • DNA forms a double helix where the two strands run in

• The four bases of DNA are adenine (A), guanine (G), antiparallel directions to one another. Page 82

cytosine (C), and thymine (T). Page 79 • In a DNA double helix, A pairs with T, and G pairs
• Adenine and guanine are purines, which are bases with a with C. Page 83

double-ring structure. Page 79

• Cytosine and thymine are pyrimidines, which are bases LG 5.4 DNA and RNA have similarities and
with a single-ring structure. Page 79 differences.

• Nucleotides in DNA incorporate the sugar deoxyribose. • RNA, like DNA, is a polymer of nucleotides linked by

Page 79 phosphodiester bonds. Page 83
• Unlike DNA, RNA incorporates the sugar ribose instead

LG 5.2 Phosphodiester bonds join nucleotides to of deoxyribose and the base uracil instead of thymine.
form nucleic acids. Page 84

• Successive nucleotides are linked by phosphodiester • DNA is typically double stranded, while RNA is typically
bonds to form a linear strand of DNA. Page 79 single stranded. Page 84
Key Terms

Nitrogenous base Cytosine (C) Antiparallel
Purine Directionality Complementary
Adenine (A) Polarity Uracil (U)
Guanine (G) 5′ end Central dogma
Pyrimidine 3′ end
Thymine (T) Double helix

Review Questions

1. Which is not a component of a nucleotide? 2. In a deoxyribonucleotide, which chemical group is
(A) A 5-carbon sugar found at the 2′ carbon of the sugar component?
(B) A phosphate group (A) An oxygen atom
(C) A nitrogen-containing base (B) A hydroxyl group
(D) A carboxyl group (C) A hydrogen atom
(D) One or more phosphate groups

MODULE 5 Nucleic Acids 85

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