Mutations in DNA and Proteins

DNA and Proteins - Mutations Summary

• Definition of Mutations: Changes to genetic material (DNA/RNA); non-coding mutations (introns) have no effect, while coding mutations (exons) may cause diseases due to dysfunctional proteins.

• Types of Mutations:

  • Base Substitution/Point Mutation: One nitrogenous base replaces another; can be silent (no effect), missense (different amino acid), or nonsense (early stop codon).

  • Base Insertion: Addition of nitrogenous bases; leads to frame-shift mutation affecting subsequent codons and protein function.

  • Base Deletion: Removal of nitrogenous bases; also causes frame-shift mutations.

• Causes of Mutations:

  • Spontaneous: Errors during DNA replication or cell division.

  • Induced:

  • Ionizing radiation (e.g. X-rays, UV light)

  • Mutagenic chemicals (e.g. from cigarettes, food, environment)

  • Viruses embedding DNA into host chromosomes (e.g. HPV).

• Germline vs. Somatic Mutations:

  • Germline: Inheritance through gametes; affects future generations.

  • Somatic: Non-inheritable; affects body cells only.

• Effects of Chromosomal Mutations: Can affect multiple genes, leading to greater individual effects (e.g., Down syndrome - extra chromosome 21).

• General Impact of Mutations: Mostly harmful due to random nature; potential sources of variation for evolution.

• Beneficial Mutation Example: CCR5-Delta 32 gene mutation confers resistance to HIV.

• Additional Disorders:

  • Tay-Sachs: Mutation in HEXA gene results in dysfunctional enzyme, leading to severe neurological issues.

  • PKU: Mutation in PAH gene affects phenylalanine metabolism, leading to mental retardation without dietary control.

  • Sickle Cell Anemia: Hemoglobin gene mutation alters red blood cell shape and function.

  • Cystic Fibrosis: Faulty gene for mucus channel protein causing respiratory and digestive issues.