Gene-Mutations

Definition of Mutation

  • Mutation: Changes in nucleotide sequences of DNA or RNA, which may affect gene function.

Spontaneous vs. Induced Mutations

  • Spontaneous Mutations: Can occur naturally during DNA replication.

  • Mutagens: Physical or environmental agents that induce mutations; examples include:

    • Pesticides

    • Tobacco Smoke

    • X-rays

    • UV rays

    • Radiation

    • Chemicals

Mechanism of Inheritance

  • Gene Mutation Inheritance:

    • Mutations can be passed to every cell that develops from the altered gene but will only affect the next generation if occurring in sperm or egg cells.

Types of Gene Mutations

Point Mutations

  • Definition: Changes in a single nucleotide, also known as substitution mutations.

  • Example: Transition of UUU to UCU codon.

Classifications of Point Mutations

  1. Silent Mutation: Mutated codon encodes the same amino acid.

    • Example: CAA (glutamine) → CAG (glutamine), Effect: None

  2. Missense Mutation: Mutated codon changes to an amino acid.

    • Example: CAA (glutamine) → CCA (proline), Effect: Variable

  3. Nonsense Mutation: Changes codon to a premature stop signal.

    • Example: CAA (glutamine) → UAA (stop), Effect: Usually serious

Sickle Cell Anemia

  • A blood disorder caused by a point mutation in the β-globin chain of hemoglobin, leading to a change from glutamic acid (hydrophilic) to valine (hydrophobic).

  • Effects include rigid, sickle-shaped red blood cells, decreased elasticity, and potential health complications.

Frameshift Mutations

  • Definition: Insertions or deletions of nucleotides that alter the reading frame of the genetic code.

    • Types:

      • Insertion Mutation: Addition of a nitrogen base.

      • Deletion Mutation: Removal of a nitrogen base, affecting protein synthesis and potential disorders, such as cystic fibrosis.

Cystic Fibrosis

  • Caused by a deletion of a single T base, leading to symptoms including difficulty breathing and production of thick mucus.