1. DNA

2. What is DNA? A code in the cell that contains the hereditary material
The code is a chemical called deoxyribonucleic acid
Every cell in your body contains DNA

3. DNA Structure
Rosalind Franklin discovered that DNA is two chains of molecules in a spiral form by using an X-ray
Similar to twisted ladder
James Watson & Francis Crick made a model of DNA molecule

4. A DNA Model
Each side of the ladder is made of sugar-phosphate molecule
Called the “backbone”
Sugar = deoxyribose

5. Rungs of the ladder are made up of nitrogenous bases
There are four types of bases
Adenine (A)
Guanine (G)
Cytosine (C)
Thymine (T)

6. Base Pairing Adenine always pairs with Thymine A-T
Cytosine always pairs with Guanine
C-G

7. Copying DNA The two sides of DNA unwind and separate
Each side becomes a pattern for a new DNA strand

9. Genes DNA in your cells stores the instructions for making proteins
Each chromosome contains hundreds or thousands of genes

11. Making Proteins
Genes are found in the nucleus, but proteins are made on ribosomes in the cytoplasm
The code for making proteins are carried from the nucleus by RNA or Ribonucleic Acid

13. Ribonucleic Acid U = Uracil RNA is different from DNA
RNA is not a spiral, but one single strand
RNA has the bases A, G, C, and U not T
U = Uracil
Sugar is ribose, not deoxyribose

14. DNA VS. RNA DNA RNA STRUCTURE SUGAR BASES Double Helix Single Strand
Deoxyribose
Ribose
BASES
A, T, C, G
A, U, C, G

15. Types of RNA Messenger RNA (mRNA) Transfer RNA (tRNA)
Ribosomal RNA (rRNA)

16. Controlling Genes
Each cell only uses some of the thousands of genes to make proteins
Cells must be able to control genes by turning some genes on and others off

18. Mutations Permanent changes in the DNA sequence of a gene
These happen when the DNA is not copied correctly
They cause incorrect proteins to be made

19. Causes of Mutations
X-rays
Sunlight
Some chemicals

20. Results of Mutations Some mutations are beneficial
They add variety to the species
Many mutations are harmful and can cause death
Cystic Fibrosis
Some mutations have no effect on the organism