Rucete ✏ Biology In a Nutshell
1. What Are Mutations?
- Mutations are changes in the DNA sequence of a gene.
- They can affect the structure and function of proteins, and may be harmless, harmful, or beneficial.
2. Types of Point Mutations
a) Substitution
- One correct nucleotide is replaced with an incorrect nucleotide in the DNA sequence.
b) Deletion
- One or more nucleotides are removed from the DNA sequence.
c) Insertion
- One or more extra nucleotides are added to the DNA sequence.
d) Frameshift Mutation
- Caused by insertions or deletions that are not multiples of three.
- Shifts the reading frame and changes every amino acid after the mutation.
3. Types of Point Mutation Effects
a) Silent Mutation
- A substitution that does not change the amino acid sequence of the protein.
b) Missense Mutation
- A substitution that changes one amino acid in the protein.
- Example: Sickle-cell disease results from a missense mutation in the hemoglobin gene.
c) Nonsense Mutation
- A substitution that creates a stop codon, leading to early termination of protein synthesis.
4. DNA Repair Mechanisms
a) Proofreading
- DNA polymerase corrects errors during replication by removing and replacing mismatched nucleotides.
b) Mismatch Repair
- Detects and fixes mismatches that escape proofreading.
c) Excision Repair
- Removes damaged or mutated nucleotides caused by mutagens (e.g., UV light or chemicals).
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Biology in a nutshell