1. DNA, PROTEIN SYNTHESIS, & Mutations
Chapters 12
Pages

2. Chapter 12: Section 1 I. History A. Frederick Griffith- 1928
- Tried to figure out how bacteria made people sick.
- Heat killed, disease-causing bacteria passed “something” along to harmless bacteria.
- He called this process “Transformation.”

4. - Determined DNA is the molecule of inheritance and not proteins.
B. Oswald Avery- 1944
- Determined DNA is the molecule of inheritance and not proteins.
Did this by destroying other cell parts
piece by piece.

5. C. Alfred Hershey & Martha Chase- 1952
Hershey & Chase – determined that DNA transmits genetic information from parent to offspring, & not any other molecule
Worked with bacteriophages – viruses that invade bacterial cells
Used bacteriophages with radioactive markers (1952)

6. Structure of Bacteriophage
Protein coat –
outer covering
DNA – inner core

7. Hershey & Chase
One bacteriophage had radioactive phosphorus-32 in its DNA & was used to infect a bacterial cell
The other had radioactive sulfur-35 in its protein coat & was used to infect a bacterial cell
Both bacterial cells were examined
Only the bacteriophage with P-32 was inside the bacterial cell, proving that DNA is the material that transmits genetic info

8. Hershey and Chase

9. D. Erwin Chargaff- Late 1940’s
Found there are 4 bases in a DNA molecule
Adenine, Guanine, Cytosine and Thymine
Found that the amount of A = T and G = C

10. E. Rosalind Franklin (1952)
Franklin used X-ray diffraction to get information about the structure of DNA
Was able to tell that DNA had an “X” like structure where the strands are twisted around each other
All of these discoveries
led to the following….

11. F. Watson and Crick
- The discovery of the structure of DNA was made in 1953 by two scientists named James Watson & Francis Crick.
- Watson & Crick proposed that DNA is shaped like a “twisted ladder.”
- This twisted ladder is also called a “Double Helix.”
- They used the
findings of the other
scientists for their model.

12. DNA
A. What is DNA ?
Stands for Deoxyribonucleic acid
Functions:
1. Transmit genetic info. to
next generation
2. Controls all cell activities,
including protein synthesis

13. B. Structure of DNA
- DNA is made of nucleotides.
1. Nucleotides consist of the following:
a. Deoxyribose – a sugar
b. A Phosphate Group
c. A Nitrogen Base
1. Four possibilities
a. Adenine (A)
b. Guanine (G)
c. Cytosine (C)
d. Thymine (T)

14. - These nucleotide bases join together to form a long single strand.
- Each long single strand of nucleotides connects to “another” single strand of nucleotides.
- The two strands are held together by hydrogen bonds.

16. C. Base Pairing Rules
1. Adenine always pairs with Thymine.
2. Cytosine always pairs with Guanine.
- The different order of these bases is what makes organisms different
This is the genetic code!
Example:
Strand 1: A – G – T – T – C – T – A – G Strand 2: T – C – A – A – G – A – T – C
Sample Exercise:
Strand 1: C – G – A – T – G – T – A – C
Strand 2: – – – – – – –

17. Sample Exercise:
Strand 1: T – C– A – A – C – G – C – C
Strand 2: – – – – – – –
- The more closely related two organisms are the more alike the order of their nucleotides in their DNA will be.
Example:
Humans  Chimps Gorillas Orangutans

18. Purines vs. Pyrimadines
Adenine and Guanine are PURINES
Thymine and Cytosine are PYRIMIDINES
Remember:

19. Purines and Pyrimidines
Purines can only pair with pyrimidines due to their size and shape.

20. III. DNA Terminology
A. Chromosomes
- Tightly compacted strands of DNA found when a cell is dividing! (Needs to be compact to fit in a small space!)
- Hold all genetic information.
- Chromosomes are passed on to an offspring by its parents.
Examples: Fruit Fly = 8
Humans = 46 Shrimp = Chimps = 48 Chicken = 78
Gorilla = 48 Wolf = 78

21. B. Chromatin
- When a cell is not dividing, DNA is in the form of chromatin.
- Loosely packed DNA that is wrapped around proteins (called histones)

22. C. Genes
- A section of DNA on a chromosome that codes for a specific protein.

23. IV. DNA Replication SECTION 2
A. DNA is copied before a cell divides so that each new cell has it’s own genetic copy.
B. There are 4 main steps:
STEP 1:
- DNA is unzipped by the enzyme HELICASE and now two single strands begin to unwind.
- Hydrogen bonds are broken.
- This is called a replication fork

24. STEP 2:
- Each unwound strand of DNA acts as a
template to produce two new strands of DNA.
STEP 3:
- An enzyme named DNA Polymerase will read each unwound strand and join new complimentary nucleotides to each.

25. - This occurs until the whole strand is replicated.
STEP 4:
- This occurs until the whole strand is
replicated.
- Now there are two
identical DNA molecules.
- Each strand contains
one original and
one new complimentary
strand.
Click image for animation!