1. DNA!

2. WHAT ARE GENES MADE OF?
Protein?
20 amino acids
Lots of different molecules could be made, enough to provide all the information to make an entire human
DNA?
Only 4 base pairs
Can enough different combinations of these provide all the information to make an entire human?

3. Griffith’s Experiment

4. BACTERIOPHAGE

6. HERSHEY AND CHASE EXPERIMENT

7. THE ROLE OF DNA (deoxyribo nucleic acid)
Storing information
All of the information needed to make an entire organism
Copying information
W hen cells divide, both cells must have a complete copy of the original cell’s DNA
Transmitting information
Information is passed from parent to offspring in DNA

8. Where is DNA found?

9. DNA: WHAT IS IT MADE OF? It is a polymer, made of nucleotides
Adeninine (A)
Guanine (G)
Cytosine (C)
Thymine (T)

10. What is that ‘base’?
It is a nitrogenous base, which means it contains N
The base is joined to the sugar by covalent bonds
The sugar is joined to the phosphate by covalent bonds
Bases are joined to each other by hydrogen bonds

11. In your notes pages, color the hydrogen bonds one color, and color the covalent bonds another color:

12. How did scientists figure out that DNA was a double helix?
Rosalind Franklin
X ray crystallography

13. Years before Franklin’s discovery, Chargaff determined that all DNA, whether it came from a human or a plant or a mushroom, had equal percentages of:
G and C
A and T

14. Watson and Crick

15. April 25, 1953
Nature

17. Let’s look at the structure of DNA:

18. Now, let’s look at the structure of DNA in detail:

19. In your ppt notes, label this diagram of DNA:
(label the nitrogenous bases, sugars, phosphates, covalent bonds, and hydrogen bonds)

20. DNA is anti-parallel

21. DNA exhibits complementary base pairing:
G always pairs with C
A always pairs with T

22. Remember what Dr. Chargaff said?
Do the following problems:
In a DNA molecule, if 20% of the bases are A, what percent of the bases are T? Show your work here:
In the same DNA molecule, what percentage of the bases are G? Show your work here:

24. How does DNA copy itself?
DNA REPLICATION!!!
During S phase of Interphase
Both mitosis and meiosis

25. The PROCESS:
First, the DNA ‘unzips’, separating each base

26. Second, new nucleotides are added to each unzipped strand of DNA:

27. New nucleotides are added in a specific way:
New As pair with the Ts on the original strand
New Ts pair with the As on the original strand
New Gs pair with the Cs on the original strand.
New Cs pair with the Gs on the original strand

28. The strand pictured at the right above is ONE of the strands that will be made from the replication of the DNA at the left. On the next slide page, draw and label the other strand that will be made:

29. 2nd DNA STRAND drawing:

30. There is a difference between how Prokaryotes replicate their DNA, and how Eukaryotes replicate their DNA: