1. DNA History, Structure, and Replication

2. DNA Today

3. PART I
The History of DNA

4. Chargaff’s Rule Adenine must pair with Thymine
Guanine must pair with Cytosine
Bases form weak hydrogen bonds T A G C

5. DNA Structure Rosalind Franklin took an
x-ray diffraction photograph of DNA.
This photograph was later used to determine DNA’s double helix structure

6. DNA Structure
In the 1950’s, Watson & Crick built the first model of DNA using Franklin’s x-rays

7. Rosalind Franklin and Watson & Crick

8. The History of DNA
One of the most recent major advances in DNA history was the Human Genome Project in 2000!!

9. Components and Structure of DNA
PART II
Components and Structure of DNA

10. DNA Deoxyribonucleic Acid
Two strands coiled = double helix

11. DNA Deoxyribonucleic Acid
Sides =
pentose sugar Deoxyribose
bonded to phosphate

12. DNA Deoxyribonucleic Acid
Rungs (center) =
nitrogen bases bonded together by:
weak hydrogen bonds

13. DNA: Deoxyribonucleic acid
Made up of subunits called nucleotides
Nucleotide made of:
1. Phosphate group
2. 5-carbon sugar
3. Nitrogenous base

14. DNA Nucleotide O O=P-O N CH2 O C1 C4 C3 C2 Phosphate Group 5
Nitrogenous base
(A, G, C, orT)
CH2 O C1 C4 C3 C2 5
Sugar
(deoxyribose)

15. DNA P O 1 2 3 4 5 P O 1 2 3 4 5 G C T A

16. History Review

17. PART III
DNA Replication

18. Replication Facts DNA has to be copied before a cell divides
DNA is copied during the S or synthesis phase of interphase
New cells will need identical DNA strands

19. Synthesis Phase (S phase)
S phase during interphase of the cell cycle
Mitosis
-prophase
-metaphase
-anaphase
-telophase G1 G2 S
phase
interphase
DNA replication takes
place in the S phase.

20. DNA Replication Begins at Origins of Replication
New strands grow at the forks
Replication
Fork
Parental DNA Molecule 3’ 5’

22. Question: DNA 5’-CGTATG-3’
What would be the complementary DNA strand for the following DNA sequence?
DNA 5’-CGTATG-3’

23. Answer:
DNA 5’-GCGTATG-3’
DNA 3’-CGCATAC-5’

24. DNA Damage & Repair
Chemicals & ultraviolet radiation damage the DNA in our body cells
Cells must continuously repair DAMAGED DNA

25. Chromatin, Chromosomes, and Genes Structure
Chromatin: DNA and protein tightly packed together
Histones: proteins that DNA wraps around
HISTONES
DNA

26. Chromatin, Chromosomes, and Gene Structure
Chromosomes: Chromatin packs tightly together to form the chromosomes that you see in mitosis during the cell cycle.
Genes: Specific pieces of DNA that code for specific traits.

27. Wrap Up
In the end of DNA replication, each OLD strand of DNA has been COPIED to produce two NEW strands.