DNA replication and DNA repair
Learning Outcomes
1. Outline the correct model of DNA replication
2. Explain how a DNA strand grows in the 5’-to-3’ direction
3. Describe the proofreading mechanisms
DNA
Formed of Nucleotides
The nucleotide is the repeating structural unit of DNA [and RNA]
DNA has 3 components…
1. Deoxyribose sugar [a pentose sugar]
2. At least one phosphate group
3. Cyclic, Nitrogenous base
a. Pyrimidine bases have a single ring structure: Thymine [T], Cytosine [C]
and Uracil [U]
b. Purine bases have a double ring structure: Adenine [A] and Guanine [G]
Structure of a DNA strand
Phosphate group connects 2 sugar molecules via ester bonds = PHOSPHODIESTER BOND!!!
o Therefore nucleotides within a strand can’t shuffle
Phosphates and sugar molecules form the backbone of DNA or RNA strand
Bases project from the backbone
Backbone is negatively charged due to negative charge on each phosphate
Learning Outcomes
1. Outline the correct model of DNA replication
2. Explain how a DNA strand grows in the 5’-to-3’ direction
3. Describe the proofreading mechanisms
DNA
Formed of Nucleotides
The nucleotide is the repeating structural unit of DNA [and RNA]
DNA has 3 components…
1. Deoxyribose sugar [a pentose sugar]
2. At least one phosphate group
3. Cyclic, Nitrogenous base
a. Pyrimidine bases have a single ring structure: Thymine [T], Cytosine [C]
and Uracil [U]
b. Purine bases have a double ring structure: Adenine [A] and Guanine [G]
Structure of a DNA strand
Phosphate group connects 2 sugar molecules via ester bonds = PHOSPHODIESTER BOND!!!
o Therefore nucleotides within a strand can’t shuffle
Phosphates and sugar molecules form the backbone of DNA or RNA strand
Bases project from the backbone
Backbone is negatively charged due to negative charge on each phosphate
