1. Chapter 4 – Genes & DNA

2. Section 1 – What Does DNA Look Like
Genes
Gives instructions for building and maintaining cells
Able to be copied so cell can divide

3. Nucleotides DNA made of subunits called nucleotides
Each nucleotide has:
Sugar
Phosphate
Base
4 Nucleotides due to 4 different bases
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)

4. Key Players Erwin Chargaff Rosalind Franklin 1950s biochemist
Chargaff’s Rules
Amount of adenine = amount of thymine
Amount of guanine = amount of cytosine
Rosalind Franklin
X-ray diffraction to see DNA molecules
DNA has a spiral shape

5. Key Players Cont’d James Watson & Francis Crick Used Franklin’s images
DNA is a long, twisted ladder
Made the double helix model
Francis Crick
James Watson

6. DNA Structure Double helix - twisted ladder model Sides of ladder
Alternating sugar and phosphate parts
Rungs of ladder
Pairs of bases
A + T OR C + G

8. Copying DNA Replication – making copies of DNA
Base pairs are complementary
Each base only pairs with its corresponding base
AT or CG
For example:
ATGCA only pairs with TACGT

9. Replication DNA molecule is “unzipped” down the middle
Ladder rungs are cut in half
Complementary nucleotides are added to the 2 strands
1/2 of DNA molecule is “old” DNA and 1/2 is “new” DNA
Proteins in the cell control the replication process

10. Section 2 – How DNA Works
Every cell in your body has about 2 meters or 6 feet of DNA!
Packaging DNA
Wound around proteins – histones
Coiled into strands
Bundled into chromosomes
Gene – a string of nucleotides

12. Genes & Proteins DNA read in 1 direction from one end to other
Amino acids
Groups of 3 bases give code to form amino acid
For example – CCA is code for amino acid proline
20 different amino acids
Human body can only produce 10
Other 10 come from our food – Essential amino acids
Proteins – long strings of amino acids linked together

13. Proteins & Traits Proteins have several functions
Chemical triggers
Messengers for processes in a cell
Proteins help determine traits
Genes are the codes for making proteins

14. RNA & Making Proteins RNA – Ribonucleic acid
Molecule that helps make proteins
Messenger RNA – mRNA
Copy of a piece of DNA
Moves from nucleus into cytoplasm
Goes into ribosome 3 bases at a time
Transfer RNA – tRNA
translates RNA message into protein
Specific tRNA molecules have certain amino acids attached
tRNA matches up with complementary bases on mRNA
Amino acids released by tRNA
Amino acids link up to produce a protein

15. protein
mRNA
DNA strand copied in nucleus
tRNA
amino acid

16. Mutations
Mutation – change in the nucleotide-base sequence in the gene or DNA molecule
3 kinds of mutations
Substitution – wrong base used
Insertion – extra base added in
Deletion – base left out

17. Do Mutations Matter? Mutation – change in a gene or DNA
3 possible outcomes
Improved trait
No change
Harmful trait
Most errors are fixed by proteins
Some become part of genetic code
Mutation in sex cells are passed on to offspring

18. How do Mutations Happen
Regularly due to random errors during replication
Mutagens – physical or chemical agents that cause mutations
High energy radiation – x-ray, UV ray, cosmic ray
Asbestos
Cigarette smoke
Harmful mutations – sickle cell disease, cancers

19. Genetic Engineering Manipulating individual genes in organisms
Create new products
Bacteria engineered to produce drugs
Plants or animals bred for superior qualities
Gene therapy
Replace defective genes with healthy genes
Are there possible dangers?

20. Genetic Identification
DNA Fingerprinting – identify unique pattern in each person’s DNA
Crime scenes
Family relationships
Trace hereditary disease

21. Cloning Clone is an exact copy of another organisms DNA
Identical twins are genetic clones
3 types of cloning
Somatic cell nuclear transfer – put DNA from one cell into another cell to create an exact copy of the original organism
DNA cloning – put a piece of DNA into another organism. Fluorescent DNA from jellyfish into bacteria to make the bacteria glow
Therapeutic cloning – produce human embryos for medical research using stem cells
Scientific and ethical issues surrounding cloning