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Ch.17 Nucleic Acids and Protein Synthesis
Timberlake - Chemistry: An Introduction to General, Organic, and Biological Chemistry 14th Edition
Timberlake14th EditionChemistry: An Introduction to General, Organic, and Biological ChemistryISBN: 9781292472249Not the one you use?Change textbook
All textbooksTimberlake 14th EditionCh.17 Nucleic Acids and Protein SynthesisProblem 106
Chapter 17, Problem 106

 In DNA, how many hydrogen bonds form between guanine and cytosine?

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Understand the structure of DNA: DNA is composed of nucleotide pairs, where each pair consists of a purine base (adenine or guanine) and a pyrimidine base (thymine or cytosine). These bases are connected by hydrogen bonds.
Recall the base pairing rules: Guanine (G) pairs with cytosine (C), and adenine (A) pairs with thymine (T). This pairing is specific and follows the Watson-Crick model.
Examine the hydrogen bonding between guanine and cytosine: Guanine and cytosine form three hydrogen bonds due to their complementary functional groups. Guanine has donor and acceptor sites that align perfectly with cytosine's donor and acceptor sites.
Visualize the bonding: The three hydrogen bonds between guanine and cytosine occur at specific locations: one between the amino group of cytosine and the carbonyl group of guanine, one between the nitrogen atom of cytosine and the hydrogen atom attached to the nitrogen of guanine, and one between the oxygen atom of cytosine and the hydrogen atom attached to the amino group of guanine.
Conclude the importance of these bonds: The three hydrogen bonds between guanine and cytosine contribute to the stability of the DNA double helix, making GC pairs stronger than AT pairs, which only form two hydrogen bonds.

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Key Concepts

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

Hydrogen Bonds in DNA

In DNA, hydrogen bonds are crucial for stabilizing the double helix structure. These bonds form between complementary nitrogenous bases, which are the building blocks of DNA. The specific pairing of bases is essential for accurate DNA replication and transcription.
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Base Pairing Rules

The base pairing rules dictate that guanine pairs with cytosine (G-C) and adenine pairs with thymine (A-T) in DNA. This specific pairing is due to the number of hydrogen bonds formed: G-C pairs form three hydrogen bonds, while A-T pairs form two. This difference in bonding strength contributes to the overall stability of the DNA molecule.
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Structure of DNA

DNA is structured as a double helix, consisting of two strands that wind around each other. Each strand is made up of a sugar-phosphate backbone and nitrogenous bases that extend inward. The arrangement of these bases and the hydrogen bonds between them are fundamental to the genetic information encoded in DNA.
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Related Practice
Textbook Question

What is similar about the primary structure of RNA and DNA?

Textbook Question

 If the DNA double helix in salmon contains 28% adenine, what is the percentage of thymine, guanine, and cytosine?

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Textbook Question

Write the complementary base sequence for each of the following DNA segments:

c. G G C C T A C C T T A A C G A C G

Textbook Question

Match the following statements with rRNA, mRNA, or tRNA:

a. combines with proteins to form ribosomes

Textbook Question

Draw the condensed structural formula for CMP.

Textbook Question

Match the following statements with rRNA, mRNA, or tRNA:

c. carries genetic information from the nucleus to the ribosomes