DNA slideshow

1. DNA

3. DNA
1. STRUCTURE
2. FUNCTION/PRODUCT
3. GENETIC CODE
4. REPLICATION

4. DNA
Deoxyribo-
Nucleic
Acid

5. 1953
James Watson = American biologist
Francis Crick = British physicist

6. Rosalind Franklin x-ray expert. Died at
age 37… no recognition for her work

7. Photo 51 shows x-ray pattern from DNA.
Watson and Crick used this to come up with
their double-helix model of DNA

8. 1. STRUCTURE OF DNA
“Double Helix”

9. -Sugar-Phosphate Backbone (rails)
-Nitrogen Bases (rungs)

10. Sugar 
1 Sugar
1 Phosphate
1 Base
Nitrogen
BasesPhosphate 
Phosphate 
Phosphate 
Phosphate 
Sugar 
Sugar 
Sugar 
Sugar 
 Nucleotide

11. Bases:
A T
G C
A=Adenine
T=Thymine
C= Cytosine
G=Guanine

12. Sugar 
Phosphate 
Nitrogen Base
Macromolecule?
1
2
3
Nucleotide
Nucleic Acid

13. “Base Pairing”
Hydrogen Bond
Purines
A, G
Pyrimidines
T, C

14. Uncoil DNA in
1 Diploid Cell =
1.7 meters
6 billion base pairs
Double
Helix

15. DNA thread from All cells in body =
Reach Moon 6000x
= 1.4 billion miles of DNA
In your body
240,000 miles  Moon
50 trillion cells

16. DNA
1. STRUCTURE
2. FUNCTION/PRODUCT
3. GENETIC CODE

17. 2. FUNCTION OF DNA
What is the function?
= Code for “Proteins”

18. Proteins = Characteristics

19. Chromosome
DNA
Gene

20. Humans have
About 20,000
Genes… we think!
 Gene (hair color)
 Gene (eye color)Diploid or Haploid?

21. Dad Mom
Dad Gene + Mom Gene = Characteristic
(Brown Hair)

22. Each Gene is
responsible for
the production
of ONE protein
Gene  Protein

23. Genes can be dozens  hundreds of letters long
= Brown hair

24. 3 bases = “Codon”
ACTGTTCGAGCTTATCodon Codon Codon Codon Codon
Codon  codes for one Amino Acid
Amino Acids  join to make Protein
1 Gene (Hair Color)
DNA
STRAND 



25. Genetic Story
4 letters
64 words = codons
20 sentences = amino acids
Story = proteins
“Human” story

26. Same Letters
A  T
G  C


Same AA
Same Proteins

27. Genetic Code = “Universal Code”
Same letters Same words = Different stories

28. Are all living things related ?

29. Do we all share a
common ancestor ??

30. DNA REPLICATION
the copying of DNA

31. No copying = no life
possible…why??

32. Complementary
Strands
Template
Strands
“Helicase”
“One old and One New”





Parent
New


“DNA polymerase”

33. Bacteria (E. coli) =
Less than 1 hour to copy 5 million base pairs (single chromosome) and divide
Human =
Few hours to copy 6 billion base pairs and divide
Only one error per billion nucleotides

34. DNA polymerases = reads and places nitrogen bases
Bacteria = 500 neucleotides/second
Humans = 50/second
Helicase = untwists and separates the template DNA strands at the replication fork

35. MUTATIONS… changes in
DNA caused by things called
mutagens

36. MUTATIONS… changes in
DNA caused by

37. The #1 cause of Mutations
• DNA makes mistakes while copying itself.

38. After a mutation… the Wrong
recipe = wrong protein. See
person 3 below.

39. Example of a gene mutation causing disease.
Sickle cell anemia.
Normal red blood cell ( left )
sickle cell shape ( right

40. Mistakes during the initial pairing of template nucleotides and complementary
nucleotides occurs at a rate of one error per 10,000 base pairs
DNA polymerase proofreads each new nucleotide against the template
nucleotide as soon as it is added
If there is an incorrect pairing, the enzyme removes the
wrong nucleotide and then resumes synthesis
The final error rate is only one per billion nucleotides
Mistakes?

41. HUMAN
GENOME

42. END