1. DNA and RNA Replication
Unit 6

2. Something to think about..
When a species reproduces, there is genetic continuity maintained from one generation to the next.
WHAT is responsible for this continuity?
HOW does this continuity happen?

3. What is DNA? DNA = DeoxyriboNucleic Acid
Genetic material present in ALL organisms
Different for each individual
Found in nucleus
Polymer- nucleic acids
Monomer = nucleotides
What three ‘parts’ are
nucleotides made of?
a. Phosphate group
b. Sugar
c. nitrogen base (A,T,C,G)

4. Nucleotides Monomer made of the following 3 parts:
1. a 5-Carbon sugar group (deoxyribose)
2. a phosphate group
3. a nitrogen base – 4 different possibilities!
(5 Carbon sugar)

5. 4 Nitrogen Bases “Pure As Gold” Purines Pyrimidines Adenine, Guanine
Cytosine, Thymine
A, G
C, T
2 carbon rings
1 carbon ring
“Pure As Gold”

6. Nitrogen Base Pairing Adenine ALWAYS pairs with Thymine
2 hydrogen bonds
Cytosine ALWAYS pairs with Guanine
3 hydrogen bonds
“AT C-G”

7. DNA Code
The order of the 4 nitrogen bases is what causes each individual’s DNA to be unique!
Pictured below are small segments of DNA from three organisms, how do they compare?
Plant Mammal Bacteria

8. DNA Code
If we looked at the total DNA of each of the below organisms, which would have DNA with the least amount of base pairs? Why?
Plant Mammal Bacteria

9. Structure of DNA
Double Helix

10. Double Helix
Which 2 scientists are credited with the discovery of the structure of DNA?
James Watson & Francis Crick (1953)
Double Helix
Nobel Prize for Medicine in 1962

11. Structure of DNA Double Stranded
“Backbone” = alternating phosphates and sugars (deoxyriboses)
Middle Portion = bases
A-T (bonded by 2 H-bonds)
C-G (bonded by 3 H-bonds)
In 3D: forms twisted ladder (spiral staircase)

12. Double Helix

13. On the diagram on the right, circle 1 nucleotide

14. DNA Replication DNA copying Why? 4 Steps
in order for genetic material to be passed on to the next generation and to preserve genetic continuity
4 Steps

15. DNA Replication “Unzip DNA twisted ladder” (HELICASE)
Break H bonds between bases

16. DNA Replication
Match correct nucleotides according to base pair rules (DNA POLYMERASE)
There are free floating nucleotides in nucleus
Remember: A-T, G-C

17. DNA Replication
Bonding-hydrogen bonds form between bases; and phosphates bond to sugar molecules to form the ‘backbone’ of DNA
Bonding continues until 2 new strands have completely formed
RESULT = 2 copies of the original DNA molecule

18. DNA Replication
Pink = parent strand Blue = daughter strands

19. DNA Replication
DNA Replication Simulation