1. DNA

2. Deoxyribonucleic Acid
Defined: Molecule that stores genetic information
Monomer: Nucleotide
Millions of nucleotides bond to make nucleic acids
Gene: section of DNA that holds instructions to build a protein

3. Nucleotide Structure A G G C T Three parts Sugar molecule
Phosphate group
Nitrogen base
(A, T, C, or G)
Nucleotides combine to make nucleic acids
A pairs with T
C pairs with G G C G C C G T A

4. Nucleotides?
How many

5. Sugar (Deoxyribose) connects with the phosphate group
4 Different Bases:
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
Chargaff’s Rules:
Rule: amount of A = amount of T
Rule: amount of C = amount of G
Human DNA: ~3 billion pairs
Nucleotides C T A A T G T

6. Double Helix
James Watson and Francis Crick identified DNA’s structure in 1953
Double Helix: spiral shape of DNA
Nucleotide strands are connected by a hydrogen bond

7. DNA Replication Defined: Process of copying DNA
During interphase (S-stage)
Step 1: DNA Helicase “unzips” the two DNA strands (breaks the H bonds)
Step 2: Free floating nucleotides (A, T, C, G) match up
Step 3: DNA Polymerase reconnects the two strands

8. T A A T G C G C A T C G T A A T G C G C C G T A C G A T DNA Helicase
polymerase
Step 1:
DNA Helicase “unzips” the two DNA strands (breaks the H bonds) T A A T
Both DNA molecules are identical
Both DNA molecules contain one original strand and one new strand.
This is called the:
semiconservative model G C G C A T C G
Step 2:
Free floating nucleotides (A, T, C, G) match up T A A T G C G C
Step 3:
DNA Polymerase reconnects the two strands C G T A C G A T
DNA Polymerase
DNA
Helicase

9. DNA Replication Video Clip

10. Accuracy & Repair A T T A T A C G A C T C G G C
Mutation: change in DNA sequence
Mutations can be corrected
Enzyme “proofreads” DNA and check/correct errors
Pre-repair: 1 in 10,000 nucleotides has an error
Post-repair: 1 in 1 billion nucleotides has an error T A T A C G
enzyme A C T C G G C

11. The Secret of Our Lives: The Human Genome Project

12. Code For Life: The Human Genome

13. Review Name the three parts of a DNA nucleotide.
Name the four nitrogen bases.
List Chargaff’s rules.
Fill in the missing DNA nucleotides:
A C ? T ? ? ? G C T ? ? A ? C ? T T
? ? C ? T A T ? ? ? C A ? G ? G ? ?
List what takes place during the three stages of DNA replication.
What type of organic moleules are DNA helicase and DNA polymerase?
Why is DNA replication considered semiconservative?
Where is the DNA mutation?
T A G G C C T G T C G A A C A G T
A T C C G G A C A A C T T G T C A