1. DNA –The Language Of Life
Chapter 11

2. 11.1 What is the chemical in genes?
Computer keyboard analogy.
100+ keys ; it’s all about the order.
Students in the classroom.
Same parts
Same chemicals.
It’s the combination =the many different characteristics.
Chemicals form DNA.

3. DNA is the chemical of genes
What does DNA do in cell cycle-
DNA replicates
DNA divides in mitosis/meiosis.
So every cell has a genetic blueprint (instructions).

4. How we know DNA is the genetic material:
Griffith’s Experiments-
Identified a Transforming Factor.
2 Strains of pneumonia bacteria.
Smooth strain- capsule.
Causes pneumonia in mice.
Rough strain - no capsule.
Does not cause pneumonia.
Heat killed smooth strain.
Combined heat-killed smooth strain and rough strain bacteria.
Caused disease in mice .

5. Griffith’s Experiment
                                                                                                                                                                           
Figure 11-1 Griffith showed that although a deadly strain of bacteria could be made harmless by heating it, some factor in that strain is still able to change other harmless bacteria into deadly ones. He called this the "transforming factor."

6. What happened? The Rough strain was transformed to become smooth.
All descendents of the transformed bacteria were smooth &caused disease.
Griffith called the substance “transforming factor”.
The substance remained active despite heating.

7. Further Experiments- identify the transforming factor
Chromosomes are made up of proteins and DNA.
Is the factor DNA or Protein?
Most scientists then-thought the hereditary material was protein not DNA.

8. Avery’s Experiment Avery used different enzymes.
Protein destroying enzymes were used on Griffith’s heat treated and live rough mixture.
Result- bacteria were transformed.
Protein was not transforming factor.
DNA destroying enzymes were used.
Result- bacteria were not transformed.
So….
DNA was the transforming factor.

9. Hershey and Chase- Bacteriophage Experiment

10. Bacteriophage -viruses that attack bacteria..
Hershey & Chase’s Bacteriophage Experiment - DNA is the genetic material
Viruses are not cells.
DNA wrapped in a protein coat.
Only reproduce in a living cell.
Viral genetic material directs host cell to make more virus.
Bacteriophage -viruses that attack bacteria..
outer coat of protein
inner core of DNA.

11. Radioactive sulfur labels protein coat.
Radioactive phosphorous labels DNA.
When phage protein coats are labeled, radioactivity was outside of the cell.
When phage DNA is labeled
radioactivity is inside the cell.
Conclusion :
phage DNA enters bacterial cell , NOT protein.
So- DNA is the genetic material !
Note-Sulfur is found in protein , not DNA.
Note- Phosphorous is found in DNA not protein.
Thus DNA is the genetic material. which direct the bacterial cell to produce new bacteriophages.

12. 11.2 Structure of DNA pp

13. Nucleic Acids-
Function - store and transfer genetic information. Genes are made of DNA.
Nucleic Acids- made up of many units of nucleotides(monomers)
Nucleotides are the building blocks.
DNA- Deoxyribonucleic Acid
4 different nucleotides.
A=adenine
G=guanine
C=cytosine
T=thymine

14. NUCLEOTIDE STRUCTURE 3 PARTS OF A NUCLEOTIDE:
Deoxyribose - 5 Carbon sugar
Phosphate Group- Phosphorous atom with 4 atoms of oxygen
Nitrogen base.
Single ring-pyrimidine
Double rings-purines

15. The 4 nucleotides of DNA:
The nitrogenous base is the difference.
Pyrimidines- single-ring structures.
Thymine- T.
Cytosine- C.
Purines- double-ring structures.
Adenine- A.
Guanine- G.
The letters T,C,A,G are used to represent the bases and also the nucleotides that contain them.

16. Sugar-phosphate DNA backbone Double helix (ladder )model
Outside of the ladder
Repeating pattern
Sugar of one nucleotide is connected to the phosphate group of the next.
Attached nitrogen bases are on the inside (rungs)of the double helix model.

17. Nucleotide chains can vary in length.
Nucleotides can combine in many different sequences represented by the letter symbols.
CTAGCCTTGAC
Nitrogenous Base Pairing:
A=T ( by 2 hydrogen bonds)
G=C (by 3 hydrogen bonds)
Called Complimentary Base Pairing.
Base-pairing rule- each base must pair up with its complementary base.

18. Double Helix Structure
1950s- Franklin- X-ray crystallography.
Showed basic shape to be a helix
1953- Watson and Crick model
Used Franklin’s photos
Twisting shape-double helix ; 2 nucleotides twist around each other.
Sugar-phosphate backbone on outside
Nitrogenous bases on the inside joined by hydrogen bonds.

19. 11.3 DNA Replication-the process of copying a DNA molecule.
Template mechanism
1.The 2 strands of the double helix separate.
DNA helicase (enzyme) “unzips” the DNA, breaking the hydrogen bonds between the base pairs.
Each strand is template for a new, complementary strand to form.
Base-pairing rules are followed.
A-T
G-C

20. DNA Replication Continued
2. DNA polymerase (enzyme)
“glues” the bonds between the nucleotides of the new DNA strand.
“proof-reads” new DNA.
DNA replication begins at specific sites called points of origin.
Replication (copying) proceeds in an outward directions from the points of origin resulting in replicating bubbles.
The parent DNA strands open up as new daughter strands grow.

21. Result of DNA replication:
Result- 2 double stranded DNA molecules;
one old & one complementary new strand.
DNA replication occurs before a cell divides.
In what stage of the cell cycle?