1. The Pieces of the Puzzle
Chapter C4
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.
DNA is made of subunits called nucleotides. A nucleotide consists of a sugar, a phosphate, and a base.

2. The Pieces of the Puzzle, continued
Chapter C4
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.

3. The Pieces of the Puzzle, continued
Chapter C4
Section 1 What Does DNA Look Like?
The Pieces of the Puzzle, continued
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.

4. DNA’s Double Structure
Chapter C4
Section 1 What Does DNA Look Like?
DNA’s Double Structure
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.

5. Chapter C4
Section 1 What Does DNA Look Like?

6. Chapter C4 Making Copies of DNA
Section 1 What Does DNA Look Like?
Chapter C4
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.

7. Making Copies of DNA, continued
Section 1 What Does DNA Look Like?
Chapter C4
Making Copies of DNA, continued

8. Chapter C4 DNA Replication Section 1 What Does DNA Look Like?
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Visual Concept