1. DNA

2. Deoxyribonucleic Acid
Defined: Molecule that stores genetic information
Monomer: Nucleotide
3 parts to nucleotide
1) Sugar
2) Phosphate Group
3) Nitrogen Base
Millions of nucleotides bond to make nucleic acids
Deoxyribonucleic
Acid

3. Nucleotides?
How many

4. Sugar (Deoxyribose) connects with the phosphate group
4 Different Bases:
Adenine (A)
Thymine (T)
Guanine (G)
Cytosine (C)
Rule: A always joins with T
Rule: C always joins with G
Human DNA: ~3 billion pairs
Nucleotides C T A A T G T

5. 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

6. 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

7. 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 G C G C A T C G
Both strands are identical
Both strands are a mix of old and new nucleotides
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

8. DNA Replication Video Clip

9. 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

10. YouTube: DNA Repair Video
Click here if video won’t play
YouTube: DNA Repair Video

11. Review T A G G C C T G T C G A A C A G T
Name the three parts of a DNA nucleotide.
Name the four nitrogen bases and how they pair with others.
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.
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