1. Ch. 12 DNA & RNA What we’ve learned so far… Cells make proteins
Instructions for how to make proteins are found in DNA
DNA is kept in the nucleus of a eukaryotic cell

2. How do genes control what you look like?
The transition...
To truly understand genetics, biologists first had to discover the chemistry in the gene.
How do genes control what you look like?

3. 12-1 DNA Vocabulary: Key Concepts: Transformation Bacteriophage
Nucleotide
Base pairing
Key Concepts:
What did scientists discover about the relationship between genes and DNA?
What is the overall structure of the DNA molecule?

4. DNA’s “Experiment” History
Pneumonia: a sickness in the lungs
Griffith: How do certain types of bacteria cause pneumonia?
The experiment that tested this question led to new knowledge.
Genetic information could be transformed from one bacterium to another.

5. Avery & DNA
Avery and a group of scientists decided to repeat Griffith’s experiment
determine which molecule in the heat-killed bacteria was needed for transformation
Made juice from heat-killed bacteria and added enzymes that destroy proteins, carbohydrates, & lipids
Transformation still occurred!
Repeated the experiment but added enzymes that destroy DNA
Transformation DID NOT occur!!

6. Genetic Info. Transferred

7. Review 1)Summarize the experiments that Griffith and Avery performed.
2) What did they find from these experiments?

8. Hershey-Chase Experiment
Studied viruses; specifically bacteriophages
Bacterio = bacteria
Phage = eater
Bacteria eater
Viruses are made up of DNA and a protein coat
Research Question: Does the protein coat or the DNA enter the infected bacteria cell?

9. Grew viruses in the presence of radioactive markers 32P and 35S.
Sulfur is found in protein coat
Phosphorus is found in DNA

10. No Sulfur!
Phosphorus!

12. Review
1) According to the Hershey-Chase experiment ___________ enters infected cells from a virus.

13. What DNA does… Carries information from one generation to the next
Put that information to work by determining what characteristics are inherited
Must be easily copied since almost every new cell gets a copy

14. DNA Structure Made up of nucleotides Each composed of 3 parts:
Deoxyribose: sugar
Phosphate group
Nitrogenous (nitrogen containing) base
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)

15. Backbone: Deoxyribose & Phosphate Group of each nucleotide
“Steps of Ladder:” bases
Any base sequence is possible

16. Oooooohhhh!! Aaaaaahhhhh!!!!
The base pairing RULES:
A = T (A pairs with T)
C = G (C pairs with G)

17. Review What is DNA made out of (remember it is a nucleic acid)?
What are the 3 parts of the building block of DNA?
What is the DNA backbone made out of?
Which bases always pair together?

18. What DNA Looks Like
Rosalind Franklin: used X-Ray diffraction patterns to discover that DNA twisted around each other like a helix

19. Watson & Crick: while trying to build a 3-D model of DNA, Watson was shown Franklin’s photograph and within weeks, figured out the structure of DNA

20. What’s holding the strands together?
HYDROGEN BONDS!!!
Hydrogen Bonds form between A and T base pairs as well as between C and G base pairs

21. Review
Describe the contributions of the following scientists to our understanding of the structure of DNA
Franklin-
Watson and Crick-
What holds DNA strands together?