Gene Mutation and Molecular Medicine

Key Concepts of Gene Mutation and Molecular Medicine

• Types of Mutations

  • Nucleotide Level:

  • Classified by changes in DNA and phenotypic effects.

  • Chromosomal Level:

  • Classified by changes in chromosomes.

• Induced Mutations:

  • Caused by mutagens (chemicals, radiation).

  • Mutation hot spots are bases more susceptible to mutations.

• Nature of Mutations:

  • Mutation: Change in nucleotide sequence that can be heritable.

  • Silent Mutations: Do not affect protein function; contribute to genetic diversity.

  • Loss of Function Mutations: Gene not expressed or protein nonfunctional; typically recessive.

  • Gain of Function Mutations: Lead to altered protein function; often dominant, can promote cancer.

• Conditional and Reversion Mutations:

  • Conditional: Phenotype changes under certain conditions.

  • Reversion: Original sequence restored by a second mutation.

• Point Mutations:

  • Change in a single nucleotide: includes transitions (purine ↔ purine, pyrimidine ↔ pyrimidine) and transversions (purine ↔ pyrimidine).

  • Can lead to effects like missense mutations (amino acid substitution), nonsense mutations (premature stop codon), and frame-shift mutations (insertion/deletion of bases).

• Chromosomal Mutations:

  • Result in extensive DNA changes: deletions, duplications, inversions, translocations.

  • Example: Down syndrome caused by translocation of chromosome 21.

• Causes of Mutations:

  • Spontaneous Mutations: Occur naturally without external influence; can be due to replication errors or base tautomerization.

  • Induced Mutations: Result from external agents like chemicals or radiation.

• Effects of Mutations:

  • Can provide genetic diversity, beneficial in natural selection.

  • Certain mutations can be deleterious, particularly in oncogenes and tumor suppressor genes.