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General Biology II: 4. Structure of DNA

General Biology II
4. Structure of DNA
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table of contents
  1. Cover
  2. Title Page
  3. Copyright
  4. Table Of Contents
  5. Reference Information
  6. The Process of Science
  7. 3. Biological Molecules
  8. 4. Structure of DNA
  9. 5. DNA Replication
  10. 6. Protein Synthesis
    1. 6.1 What are proteins and what do they do?
    2. 6.2 What is a gene?
    3. 6.3 How do genes direct the production of proteins?
    4. 6.4 Transcription: from DNA to mRNA
    5. 6.5 Eukaryotic RNA Processing
    6. 6.6 Translation
    7. 6.7 The Genetic Code
    8. Optional Section - Micropigs
  11. 7. Mutations
    1. How Gene Mutations Occur
    2. Intro to Genetic Disorders
    3. Do all gene affect health and development?
    4. Types of Mutations
    5. Changes in Numbers of Genes
    6. Changes in Chromosome Number
    7. Complex Multifactorial Disorders
    8. Genetic Predispositions
    9. Genetics and Statistics
  12. Gene Regulation
    1. 8.1 Prokaryotic versus Eukaryotic Gene Expression
    2. 8.2 What is the epigenome?
    3. 8.3 Alternative RNA splicing
  13. 9. Biotechnology
    1. 9.1 Manipulating Genetic Material
    2. 9.2 Cloning
    3. 9.3 Genetic Engineering
    4. 9.4 Biotechnology in Medicine and Agriculture
    5. 9.5 Genomics and Proteomics
    6. 9.6 Applying Genomics
    7. 9.7 Proteomics
  14. 10. Cell Division - Binary Fission and Mitosis
    1. 10.1 Prokaryotic Cell Division
    2. 10.2 Eukaryotic Cell Division
    3. 10.3 Control of the Cell Cycle
    4. 10.4 Cancer and the Cell Cycle
  15. 11. Meiosis
    1. 11.1 Sexual Reproduction
    2. 11.2 Overview of Meiosis
    3. 11.3 Interphase
    4. 11.4 Meiosis I
    5. 11.5 Meiosis II
    6. 11.6 Comparing Meiosis and Mitosis
    7. 11.7 Errors in Meiosis
  16. 12. Patterns of Inheritance
    1. 12.1 Mendelian Genetics
    2. 12.2 Garden Pea Characteristics Revealed the Basics of Heredity
    3. 12.3 Phenotypes and Genotypes
    4. 12.4 Monohybrid Cross and the Punnett Square
    5. 12.5 Laws of Inheritance
    6. 12.6 Extensions of the Laws of Inheritance
    7. 12.7 Multiple Alleles
    8. 12.8 Sex-Linked Traits
    9. 12.9 Linked Genes Violate the Law of Independent Assortment
    10. 12.10 Epistasis
  17. Genetics: Dog Coat Color
    1. Introduction to Genetics
    2. Pedigrees and Punnett Squares
    3. Black fur color: a dominant trait
    4. Yellow fur color: a recessive trait
    5. Epistasis: the relationship between black, brown, and yellow fur
    6. Brindle color: partial dominance and epistasis
    7. Incomplete dominance: when traits blend
    8. White spotting: When there's more than two alleles
    9. Hemophilia: a sex-linked disorder
    10. Overall phenotypes: putting it all together
    11. Additional complexity
    12. It's not all in the genes

4. Structure of DNA

Learning Objectives

By the end of this section, you will begin to: Discuss and apply biological theories and concepts of the molecular and genetic of life, including cell division, inheritance, and gene regulation by showing that you can:

  • Describe the structure of DNA.

DNA is the genetic material passed from parent to offspring for all life on Earth. The three letters “DNA” have now become associated with crime solving, paternity testing, human identification, and genetic testing. DNA can be retrieved from hair, blood, or saliva. With the exception of identical twins, each person’s DNA is unique and it is possible to detect differences between human beings on the basis of their unique DNA sequence.

DNA analysis has many practical applications beyond forensics and paternity testing. DNA testing is used for tracing genealogy and identifying pathogens. In the medical field, DNA is used in diagnostics, new vaccine development, and cancer therapy. It is now possible to determine predisposition to many diseases by analyzing genes.

In the 1950s, Francis Crick and James Watson worked together at the University of Cambridge, England, to determine the structure of DNA. Other scientists, such as Linus Pauling and Maurice Wilkins, were also actively exploring this field. Pauling had discovered the secondary structure of proteins using X-ray crystallography. X-ray crystallography is a method for investigating molecular structure by observing the patterns formed by X-rays shot through a crystal of the substance. The patterns give important information about the structure of the molecule of interest. In Wilkins’ lab, researcher Rosalind Franklin was using X-ray crystallography to understand the structure of DNA. Watson and Crick were able to piece together the puzzle of the DNA molecule using Franklin’s data (Figure 9.2). Watson and Crick also had key pieces of information available from other researchers such as Chargaff’s rules. Chargaff had shown that of the four kinds of monomers (nucleotides) present in a DNA molecule, two types were always present in equal amounts and the remaining two types were also always present in equal amounts. This meant they were always paired in some way. In 1962, James Watson, Francis Crick, and Maurice Wilkins were awarded the Nobel Prize in Medicine for their work in determining the structure of DNA.

Watson and Crick with Photo 51
Figure 1: Pioneering scientists (a) James Watson and Francis Crick are pictured here with American geneticist Maclyn McCarty. Scientist Rosalind Franklin discovered (b) the X-ray diffraction pattern of DNA, which helped to elucidate its double helix structure. (credit a: modification of work by Marjorie McCarty; b: modification of work by NIH)

References

Unless otherwise noted, images on this page are licensed under CC-BY 4.0 by OpenStax.

OpenStax, Concepts of Biology. OpenStax CNX. May 18, 2016 http://cnx.org/contents/s8Hh0oOc@9.10:8v2Xzdco@5/The-Structure-of-DNA

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Copyright © 2016 by Lisa Bartee and Christine Anderson. Mt Hood Community College Biology 102 by Lisa Bartee and Christine Anderson is licensed under a Creative Commons Attribution 4.0 International License, except where otherwise noted.
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