DNA Mutations
TYPES OF MUTATIONS
Substitution: single nucleotide replaced
- Point mutations
- Nonsense mutation: generates stop codon
- Missense mutation: generates incorrect amino acid
- Silent mutation: generates same amino acid
Deletion: single nucleotide removed
- Frame-shift mutation
Insertion: single nucleotide inserted
- Frame-shift mutation
- Frequency of replication errors very low (1 in 10^9 nucleotides added)
- DNA polymerase increases fidelity:
Sickle-cell anemia
- Missense mutation (adenine to thymine) changes 3D structure of hemoglobin beta-subunit
- Produces valine instead of glutamate
- Results in sickle-shaped red blood cell instead of biconcave
- Confers malaria-resistance: parasite cannot grow in mutated hemoglobin