Ch. 5 - The Structure and Function of Large Biological Molecules

Campbell - Campbell Biology 12th Edition

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Urry 12th Edition

Ch. 5 - The Structure and Function of Large Biological Molecules

Problem 7

Chapter 5, Problem 7

Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA?
a. 5′-AGCT-3′ with 5′-TCGA-3′
b. 5′-GCGC-3′ with 5′-TATA-3′
c. 5′-ATGC-3′ with 5′-GCAT-3′
d. All of these pairs are correct.

Verified step by step guidance

Understand the basic principle of DNA base pairing: In a DNA double helix, adenine (A) pairs with thymine (T), and cytosine (C) pairs with guanine (G).

Examine option a: 5′-AGCT-3′ with 5′-TCGA-3′. Check if each base pairs correctly according to the base pairing rules: A with T, G with C, C with G, and T with A.

Examine option b: 5′-GCGC-3′ with 5′-TATA-3′. Check if each base pairs correctly: G with C, C with G, G with C, and C with G. Notice that T does not pair with G, and A does not pair with C.

Examine option c: 5′-ATGC-3′ with 5′-GCAT-3′. Check if each base pairs correctly: A with T, T with A, G with C, and C with G.

Determine which pair(s) follow the correct base pairing rules and conclude whether one or more pairs can form a normal double helix of DNA.

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Key Concepts

Here are the essential concepts you must grasp in order to answer the question correctly.

DNA Structure

DNA is composed of two strands forming a double helix, where each strand consists of nucleotides with bases adenine (A), thymine (T), cytosine (C), and guanine (G). The strands are antiparallel, meaning they run in opposite directions, which is crucial for base pairing and the overall structure of DNA.

Base Pairing Rules

In DNA, base pairing follows specific rules: adenine (A) pairs with thymine (T) via two hydrogen bonds, and cytosine (C) pairs with guanine (G) via three hydrogen bonds. These complementary base pairs are essential for the stability and replication of the DNA double helix.

Antiparallel Orientation

The antiparallel orientation of DNA strands means one strand runs in the 5′ to 3′ direction, while the complementary strand runs in the 3′ to 5′ direction. This orientation is necessary for proper base pairing and the formation of the double helix, ensuring the strands align correctly for replication and transcription.

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Discovering the Structure of DNA

Related Practice

Textbook Question

The structural level of a protein least affected by a disruption in hydrogen bonding is the

a. Primary level.

b. Secondary level.

c. Tertiary level.

d. Quaternary level.

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Textbook Question

Enzymes that break down DNA catalyze the hydrolysis of the covalent bonds that join nucleotides together. What would happen to DNA molecules treated with these enzymes?

a. The two strands of the double helix would separate.

b. The phosphodiester linkages of the polynucleotide backbone would be broken.

c. The pyrimidines would be separated from the deoxyribose sugars.

d. All bases would be separated from the deoxyribose sugars.

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Textbook Question

The molecular formula for glucose is C₆H₁₂O₆. What would be the molecular formula for a polymer made by linking ten glucose molecules together by dehydration reactions?

a. C₆₀H₁₂₀O₆₀

b. C₆₀H₁₀₂O₅₁

c. C₆₀H₁₀₀O₅₀

d. C₆₀H₁₁₁O₅₁

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Textbook Question

Construct a table that organizes the following terms, and label the columns and rows.

Monosaccharides

Fatty acids

Amino acids

Nucleotides

Polypeptides

Triacylglycerols

Polynucleotides

Polysaccharides

Phosphodiester linkages

Peptide bonds

Glycosidic linkages

Ester linkages

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Textbook Question

Copy the polynucleotide strand in Figure 5.23a and label the bases G, T, C, and T, starting from the 5′ end. Assuming this is a DNA polynucleotide, now draw the complementary strand, using the same symbols for phosphates (circles), sugars (pentagons), and bases. Label the bases. Draw arrows showing the 5'→3' direction of each strand. Use the arrows to make sure the second strand is antiparallel to the first.

Hint: After you draw the first strand vertically, turn the paper upside down; it is easier to draw the second strand from the 5′ toward the 3′ direction as you go from top to bottom.

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Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA? a. 5′-AGCT-3′ with 5′-TCGA-3′ b. 5′-GCGC-3′ with 5′-TATA-3′ c. 5′-ATGC-3′ with 5′-GCAT-3′ d. All of these pairs are correct.

Verified video answer for a similar problem:

Key Concepts

DNA Structure

Base Pairing Rules

Antiparallel Orientation

Which of the following pairs of base sequences could form a short stretch of a normal double helix of DNA?
a. 5′-AGCT-3′ with 5′-TCGA-3′
b. 5′-GCGC-3′ with 5′-TATA-3′
c. 5′-ATGC-3′ with 5′-GCAT-3′
d. All of these pairs are correct.