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Chapter 9: Problem 14

Describe the various characteristics of the Watson-Crick double helix model for DNA.

Short Answer

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Answer: The four nitrogenous bases in DNA are adenine (A), guanine (G), cytosine (C), and thymine (T). According to the Watson-Crick double helix model, adenine pairs with thymine (A-T), and guanine pairs with cytosine (G-C) through hydrogen bonds.

Step by step solution

01

1. Describe the structure of DNA

DNA (Deoxyribonucleic acid) is the genetic material that contains the information required for the proper growth, development, and reproduction of an organism. The structure of DNA, as proposed by James Watson and Francis Crick in 1953, is known as the double helix model. In this model, DNA consists of two complementary strands of nucleotides, which are connected by hydrogen bonds and twisted into a helical shape. Each nucleotide contains a sugar (deoxyribose), a phosphate group, and one of the four nitrogenous bases (adenine, guanine, cytosine, or thymine).
02

2. Explain the base pairing rules

In the Watson-Crick double helix model, the two strands of DNA are held together by specific base pairing interactions between the nitrogenous bases. These base pairing rules, also known as complementary base pairing, state that adenine (A) pairs with thymine (T) and guanine (G) pairs with cytosine (C) through hydrogen bonds. A and T form two hydrogen bonds, while G and C form three hydrogen bonds, providing stability to the DNA structure.
03

3. Discuss DNA replication

The Watson-Crick double helix model plays a crucial role in understanding how DNA replicates itself. During replication, the two complementary strands of DNA separate, and each strand serves as a template for the synthesis of a new, complementary strand. The base pairing rules (A-T and G-C) ensure that the newly synthesized strands are accurate copies of the original strands and that the genetic information is preserved during cell division.
04

4. Summarize the significance of the double helix model

The Watson-Crick double helix model has provided a comprehensive understanding of the structure and function of DNA. This model has paved the way for numerous discoveries in molecular biology, genetics, and biotechnology. It has also provided a framework for understanding the molecular mechanisms of DNA replication, transcription, and translation, which are essential processes for the flow of genetic information in living organisms. Overall, the Watson-Crick double helix model has had a profound impact on our understanding of the genetic code and the molecular basis of life.

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Most popular questions from this chapter

What are the structural differences between (a) purines and pyrimidines, and (b) ribose and deoxyribose sugars?

In this chapter, we have focused on DNA, the molecule that stores genetic information in all living things. In particular, we discussed its structure and delved into how we analyze this molecule. Based on your knowledge of these topics, answer several fundamental questions: (a) How were we able to determine that DNA, and not some other molecule, serves as the genetic material in bacteria, bacteriophages, and eukaryotes? (b) How do we know that the structure of DNA is in the form of a right-handed double-helical molecule? (c) How do we know that in DNA G pairs with C and that A pairs with T as complementary strands are formed? (d) How do we know that repetitive DNA sequences exist in eukaryotes?

If the GC content of a DNA molecule is \(60 \%\), what are the molar percentages of the four bases (G, C, T, A)?

What are the three major types of RNA molecules? How is each related to the concept of information flow?

What is the physical state of DNA after being denatured by heat?
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