Define the different types of mutations that are made in the DNA sequence. What categories do they fit into? What results can occur from mutations?

Question 1

Silent Mutation

Answer 1

• Definition: A mutation that does not change the amino acid sequence or phenotype.
• Mechanism: Often occurs due to the wobble hypothesis, where the third base in a codon can vary without changing the amino acid.
• Location: Typically in non-coding regions like introns or redundant codons in coding regions.
• Result: No impact on protein function.

Question 2

Small-Scale Mutations (Point Mutations)

Answer 2

Involve changes to one or a few base pairs.

• Types:
  
  • Substitution: One base is replaced by another.
    
    • Missense Mutation:
      
      • Changes an amino acid.
      • May result in a dysfunctional or differently functioning protein.
      • Can occasionally be beneficial.
    • Nonsense Mutation:
      
      • Changes an amino acid codon to a stop codon.
      • Leads to a truncated, often non-functional protein.
  • Insertion: Adds extra base(s).
  • Deletion: Removes base(s).
    
    • Frameshift Mutation:
      
      • Caused by insertion or deletion.
      • Shifts the reading frame, changing the codons and resulting in a completely different and likely non-functional protein.

Question 3

Chromosomal Mutations

Answer 3

Affect larger DNA segments or entire chromosomes.

• Types:
  
  • Translocation:
    
    • A segment of one chromosome breaks off and attaches to another.
    • Results in the formation of entirely new gene sequences.
  • Inversion:
    
    • A section of the DNA sequence is reversed.
    • May disrupt gene function.

Question 4

Mutation Categories

Answer 4

1. Silent Mutations: No effect on protein or phenotype.
2. Missense Mutations: Alter protein structure and function.
3. Nonsense Mutations: Terminate protein synthesis prematurely.
4. Frameshift Mutations: Cause widespread changes to the protein.
5. Chromosomal Mutations: Affect large DNA regions, altering gene arrangement and expression.

Question 5

Possible Results of Mutations

Answer 5

1. Neutral Effect: No change in protein function (e.g., silent mutations).
2. Negative Effect: Dysfunctional or harmful proteins (e.g., missense, nonsense, frameshift).
3. Positive Effect: Rare cases where mutations improve protein function or provide an advantage (e.g., missense).
4. Lethal Effect: Severe disruptions to essential proteins, causing cell or organism death.