1. DNA Structure and Replication

2. Review What organelle is the “control center” of the cell? The Nucleus
What structures are found in the nucleus? Chromosomes
What are located on chromosomes? Genes

3. Review What are chromosomes made of? DNA & proteins
How do genes and chromosomes control the activity of a cell? By making proteins that regulate cellular functions or become part of the cell.

4. Frederick Griffith British scientist, 1928
Experiments with pneumonia bacteria & mice (page )
He discovered “Transformation”
Was this a gene?

5. Hershey-Chase 1952 by Alfred Hershey and Martha Chase
Used radioactive Bacteriophages (viruses) to infect bacteria (page )
Found the infecting agent to be DNA

6. Genes have to carry information from one generation to the next.
DNA has 3 jobs to do…
Genes have to carry information from one generation to the next.
They have to use the information to determine characteristics of an organism.
They have to be easily copied.
Chargaff Rules
Erwin Chargaff, American biochemist
Discovered the same amount of Cytosine and Guanine in any DNA sample & the same amount of Adenine and Thymine in any DNA sample
A = T
G = C

7. Rosalind Franklin & X-ray diffraction
1950’s, British scientist: Rosalind Franklin took pictures of DNA using X-rays.
Watson and Crick
Francis Crick & James Watson were trying to discover the structure of DNA.
Making a 3-D model
They used Franklin’s photograph to determine that it was a double helix (2 strands of DNA wound around each other)

8. Watson & Crick
Francis Crick & James Watson were trying to discover the structure of DNA.
Making a 3-D model
They used Franklin’s photograph to determine that it was a double helix (2 strands of DNA wound around each other)

9. DNA Structure A – T G - C DNA is made of units called “nucleotides”
Nucleotide = Sugar (deoxyribose) + Phosphate group + Nitrogenous base
A double helix looks like a twisted ladder.
Four kinds of nitrogenous bases:
Adenine Purines (2 rings)
Guanine
Cytosine Pyrimidines (1 ring)
Thymine
A – T
G - C

11. The two parent stands separate.
A new strand is made complimentary to each parent strand.
At the end we have 4 DNA strands.
Base pairing to original parent strands keeps the DNA the same.

12. DNA Storage DNA wraps around protein and coils into compact blobs!
This allows a lot of DNA to fit in small area.
During Mitosis the DNA coils into the chromosome shape that we are familiar with.
Outside of mitosis the DNA is coiled but not as condensed as in Mitosis