Download DNA - Miss Gleason`s Science

DNA
Discovery of DNA
• Griffith- how does bacteria cause disease?
– Injected mice with harmful and harmless bacteria
– Mice w/ harmful bacteria died
– Heated harmful bacteria injected in mice= lived
– Inject mix of heated dead harmful bacteria with
live harmless bacteria in mice= died
• Transformation- dead bacteria passed disease
causing ability to the harmless bacteria
• Hypothesized a gene
• Avery- (1944)
• DNA stores/transmits genetic info from one
gen. To the next
– Made “juice” of bacteria treated it with enzymes
that broke down RNA
• Transformation still occurred
– Repeated but with enzymes that broke down DNA
• Transformation did not occur
• Hershey and Chase
• Bacteriophages- Virus attaches to the surface
of the cell and inject its genetic info
• Used radioactive markers- phosphorus (P) and
Sulfur (S)
– Determine if the protein coat or DNA core enters
cell
• Conclusion- genetic material was DNA not
protein
DNA
• Long molecule made up of nucleotides
– 5 carbon sugar= deoxyribose
– Phosphate group
– Nitrogenous containing base
4 Nitrogenous Bases
Adenine, Guanine, Cytosine, Thymine
2 Groups
1. Purines- 2 rings
- Adenine & Guanine
2. Pyrimidines- 1 ring
-Cytosine & Thymine
DNA = Double Helix
• Rosalind Franklin- took x-rays of DNAs shape
• X-ray showed strands of DNA are twisted
around each other like coils
• Angle of the X shows there are 2 strands
• Watson and Crick- working on a model of DNA
– Saw Franklins x-ray- used her research to build
model of DNA
– Double Helix- 2 strands wound around each other
• 2 strands
• DNA backbone- sugar and phosphate group
• Middle- Nitrogenous bases pair= hydrogen
bonds
– Adenine= Thymine A-T
– Cytosine= Guanine C-G
DNA Replication
• Each strand of DNA has all of the info needed
to reconstruct the other half by base pairing
• Strands= complementary
• Replication takes place at many spots =
replication forks
Process of Replication
• DNA molecule separates into 2 strands
• Each strand serves as a template
• Produces two new complementary strands
using base pairing
1. Helicase (enzyme) unzips DNA by breaking
hydrogen bond
2. Strands unwind
3. DNA polymerase attaches and pairs
nucleotides using base pairing
• If DNA template strand is
AGTCGAAATCCTG what is the compliment
• TCAGCTTTAGGAC