1. Standardized Test Prep Image and Math Focus Bank
Resources
Chapter Presentation
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Transparencies
Standardized Test Prep
Image and Math Focus Bank
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Visual Concepts

2. Chapter 6
Section 1 What Does DNA Look Like?
Objectives
List three important events that led to understanding the structure of DNA.
Describe the basic structure of a DNA molecule.
Explain how DNA molecules can be copied.

3. The Pieces of the Puzzle
Chapter 6
Section 1 What Does DNA Look Like?
The Pieces of the Puzzle
DNA stands for deoxyribonucleic acid. DNA is the genetic material that determines inherited characteristics.
Nucleotides: The Subunits of DNA DNA is made of subunits called nucleotides. A nucleotide consists of a sugar, a phosphate, and a base.

4. The Pieces of the Puzzle, continued
Chapter 6
Section 1 What Does DNA Look Like?
The Pieces of the Puzzle, continued
Chargaff’s Rule Erwin Chargaff found that the amount of adenine in DNA always equals the amount of thymine, and the amount of guanine always equals the amount of cytosine.
Franklin’s Discovery Chemist Rosalind Franklin was able to make images of DNA molecules by using X-ray diffraction.

5. The Pieces of the Puzzle, continued
Chapter 6
Section 1 What Does DNA Look Like?
The Pieces of the Puzzle, continued
Watson and Crick’s Model James Watson and Francis Crick used Chargaff’s and Franklin’s research to build a model of DNA.
The model, which looked like a long, twisted ladder, eventually helped explain how DNA is copied and how it functions in the cell.

6. DNA’s Double Structure
Chapter 6
Section 1 What Does DNA Look Like?
DNA’s Double Structure
The Double Helix The shape of DNA is known as a double helix.
The two sides of the ladder are made of alternating sugar parts and phosphate parts.
The rungs of the ladder are made of a pair of bases.

7. Chapter 6
Section 1 What Does DNA Look Like?

8. Chapter 6 Making Copies of DNA
Section 1 What Does DNA Look Like?
Making Copies of DNA
How Copies Are Made During replication, a DNA molecule is split down the middle, where the bases meet. The bases on each side of the molecule are used as a pattern for a new strand.
When Copies Are Made DNA is copied every time a cell divides. Each new cell gets a complete copy of all the DNA.

9. Making Copies of DNA, continued
Chapter 6
Section 1 What Does DNA Look Like?
Making Copies of DNA, continued

10. Chapter 6 DNA Replication Section 1 What Does DNA Look Like?
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Visual Concept

11. Chapter 6
Section 2 How DNA Works
Objectives
Explain the relationship between DNA, genes, and proteins.
Outline the basic steps in making a protein.
Describe three types of mutations, and provide an example of a gene mutation.
Describe two examples of uses of genetic knowledge.

12. Chapter 6 Unraveling DNA
Section 2 How DNA Works
Unraveling DNA
DNA is often wound around proteins, coiled into strands, and then bundled up even more. In a cell that has a nucleus, the strands of DNA and proteins are bundled into chromosomes.
A gene consists of a string of nucleotides that give the cell information about how to make a specific trait.

13. Chapter 6
Section 2 How DNA Works

14. Chapter 6 Genes and Proteins
Section 2 How DNA Works
Genes and Proteins
Proteins and Traits Proteins act as chemical triggers for many of the processes within cells. Proteins help determine traits.
Help from RNA Another type of molecule that helps make proteins is called RNA, or ribonucleic acid. RNA is so similar to DNA that RNA can serve as a temporary copy of a DNA sequence.

15. Genes and Proteins, continued
Chapter 6
Section 2 How DNA Works
Genes and Proteins, continued
The Making of a Protein The first step in making a protein is to copy one side of the segment of DNA containing a gene. This copy is called messenger RNA (mRNA).
A ribosome is a cell organelle composed of RNA and protein. A ribosome uses mRNA, transfer RNA (tRNA), and amino acids to make proteins.
You can see the steps of protein production on the following two slides.

16. Chapter 6
Section 2 How DNA Works

17. Chapter 6
Section 2 How DNA Works

18. Chapter 6 Changes in Genes
Section 2 How DNA Works
Changes in Genes
Mutations Changes in the number, type, or order of bases on a piece of DNA are known as mutations.

19. Changes in Genes, continued
Chapter 6
Section 2 How DNA Works
Changes in Genes, continued
Do Mutations Matter? There are three possible consequences to changes in DNA: an improved trait, no change, or a harmful trait.
How Do Mutations Happen? Mutations happen regularly because of random errors when DNA is copied. Any physical or chemical agent that can cause a mutation in DNA is called a mutagen.

20. Carcinogens and Mutagens
Chapter 6
Section 2 How DNA Works
Carcinogens and Mutagens
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Visual Concept

21. An Example of Substitution
Chapter 6
Section 2 How DNA Works
An Example of Substitution
A mutation, such as a substitution, can be harmful because it may cause a gene to produce the wrong protein.
A simple change in an amino acid can cause a disease such as sickle cell anemia, as shown on the next slide.

22. Chapter 6
Section 2 How DNA Works

23. Uses of Genetic Knowledge
Chapter 6
Section 2 How DNA Works
Uses of Genetic Knowledge
Genetic Engineering Scientists can manipulate individual genes within organisms. This kind of manipulation is called genetic engineering.
Genetic Identification Your DNA is unique, so it can be used like a fingerprint to identify you. DNA fingerprinting identifies the unique patterns in an individual’s DNA.
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24. Chapter 6
Genes and DNA
Concept Map
Use the terms below to complete the concept map on the next slide.
mutation
amino acid
nucleotide
DNA
adenine
genes
guanine
proteins
chromosomes
cytosine

25. Chapter 6
Concept Map

26. Chapter 6
Concept Map

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28. Chapter 6
Section 1 What Does DNA Look Like?

29. Chapter 6
Section 1 What Does DNA Look Like?

30. Chapter 6
Section 2 How DNA Works

31. Chapter 6
Standardized Test Preparation

32. Chapter 6
Standardized Test Preparation