1. 2. Which organelle is this structure located in?
1. What structure carries genetic information from generation to generation?
2. Which organelle is this structure located in?
3. How long do you think it has taken to discover DNA and its structure? Do you think one person is responsible for the discovery?

2. DNA is the GENETIC or HEREDITARY material.
In other words, DNA is what gets “passed down” to future generations that causes us to have many of the traits we have.

3. Many important scientists contributed to the discoveries:

4. Gregor Mendel “Father of Genetics” (1822-1884)
Famous experiments with pea plants that explained patterns of inheritance
Two “units” of information- one from each parent
First scientist to acknowledge material for heredity

6. Frederick Griffith 1928
Fred was trying to find a vaccine against pneumonia, but instead made a breakthrough in world of heredity.
Frederick experimented with pneumonia in mice and found that a hereditary material caused pneumonia.

7. Determined which molecules in cells caused pneumonia to occur.
Oswald Avery, 1944
Determined which molecules in cells caused pneumonia to occur.
He separated all organic compounds inside of the cells and found only the DNA caused the disease.
*******Conclusion: DNA must be the hereditary material

8. Alfred Hershey &
Martha Chase,
1952
Skeptical of other scientists’ experiments
Wanted to be sure DNA was hereditary material

9. Rosalind Franklin,
1952
Studied structure of many microscopic viruses and cellular structures
Researched DNA – used X-RAY Diffraction to show shape of DNA= helical w/ 2 strands.
Rosalind’s lab work was stolen

10. James Watson &
Francis Crick,
1953

11. Watson and Crick’s model of DNA was a DOUBLE HELIX,
in which two strands were wound around each other.

12. The sides of the DNA “ladder” are made of SUGARS and PHOSPHATES.
So, DNA is said to have a
SUGAR-PHOSPHATE BACKBONE.

13. The rungs of the DNA “ladder” are made of a sequence of four chemicals called NITROGENOUS BASES.

14. Erwin Chargaff,
in the early 1900s,
discovered that certain chemicals in all DNA seemed to be present in almost EQUAL amounts.

15. ADENINE and THYMINE were always present in equal amounts.
GUANINE and CYTOSINE were always present in equal amounts.

16. Adenine [A] always pairs with Thymine [T]
THE BASE PAIRING RULE:
Adenine [A] always pairs with Thymine [T]
Guanine [G] always pairs with Cytosine [C]

17. All living things are made of cells...
THE BIG PICTURE
All living things are made of cells...
onion root tip

18. Each individual cell has a NUCLEUS, or at least a NUCLEAR REGION...
THE BIG PICTURE
Each individual cell has a NUCLEUS, or at least a NUCLEAR REGION...
nucleus

19. Each cell’s nucleus contains the CHROMATIN...
THE BIG PICTURE
Each cell’s nucleus contains the CHROMATIN...

20. The chromatin is composed of deoxyribonucleic acid, or DNA...
THE BIG PICTURE
The chromatin is composed of deoxyribonucleic acid, or DNA...
chromatin
DNA

21. THE BIG PICTURE
DNA is composed of a deoxyribose sugars, phosphates, and paired nitrogenous bases...
Sugar-phosphate backbone
Nitrogenous base pairs

22. The nitrogenous bases match up according to the BASE PAIRING RULE,
THE BIG PICTURE
The nitrogenous bases match up according to the BASE PAIRING RULE,
A goes with T and C goes with G