2. DNA
Deoxyribonucleic Acid
• Two strands coiled =
double helix
• Sides = pentose sugar
Deoxyribose bonded to
phosphate (PO4)
• nitrogen bases bonded
together by weak
hydrogen bonds
3. DNA:Deoxyribonucleic acid
•Made up of subunits
called nucleotides
•Nucleotide made of:
1. Phosphate group
2. 5-carbon sugar
3. Nitrogenous base
4. Nitrogenous Bases
• Double ring PURINES
Adenine (A) Guanine
(G)
• Single ring PYRIMIDINES
Thymine (T)
Cytosine (C)
Purines always pair with
Pyrimidines
4
T or C
A or G
8. 8
MechanismOf DNAReplication
Maystart at anypoint
Different stepsinvolved in replication….
1. Unwindingof DNADuplex:
Helicase enzyme
Topoisomerase
Single Stranded Binding Proteins
1. Roleof DNApolymerase:
DNA polymerase I
DNA polymerase II
DNA polymerase III
Synthesisof LeadingandLaggingstrand
9. 9
DNA Polymerase I
Replication occurs 5' to 3‘
Relatively small enzyme
Acts at NICK
Replaces RNA nucleotides in RNA primer by DNA nucleotide
DNA Polymerase II
Acts as proof reader