1. 11.1 DNA
DNA and Genes

2. What is DNA? Instructions for building proteins
Living things contain proteins in skin, muscles, bones
Proteins called enzymes are important for functions like eating, running, thinking

3. What is DNA?
DNA is the code that tells how to make proteins

4. The structure of DNA DNA is a polymer Made of nucleotides
Sugar
Phosphate group
Nitrogen base
Deoxyribonucleic acid

5. The structure of DNA nucleotides Sugar Phosphate group Nitrogen base
Adenine
Guanine
Cytosine
Thymine

6. The structure of DNA
Nucleotides join together to form long chains

7. The structure of DNA
In 1953 James Watson and Francis Crick proposed DNA is two chains joined by bonds between nitrogen bases
After seeing Rosalind Franklin’s x-ray diffraction image of DNA

8. The structure of DNA Four nucleotides code for everything
The sequence or order is important
Just like order of letters in a word
Different nucleotide sequence carries different meaning – codes for different protein

9. Replication of DNA
Before a cell divides by mitosis or meiosis a copy of the chromosomes is made

10. Replication of DNA
1. strand separates – an enzyme breaks the hydrogen bonds holding nucleotides together

11. Replication of DNA 1. strand separates
2. nucleotides that are floating free nearby bond to the single strands
3. another enzyme bonds nucleotides into a new chain

12. Get two identical DNA so when cell divides, each daughter cell has a copy

13. Coming up: more on how DNA is like a library of books and how the information is used to make proteins