DNA Mutations

DNA Mutations

Changes in the DNA sequence that can lead to variations in genes. These mutations can occur naturally or as a result of environmental factors.

natural mutations occur during…

DNA replication/recombination

• they are random & spontaneous

Large scale mutations

long segments of DNA changed via

• translocations, duplications, & inversions

Small scale mutations

small, single base segments of DNA changed via

• point mutation/substitution mutations

• 1 base incorrect in DNA = 1 mRNA incorrect

types of substitution mutations: point mutations

1. Silent mutation

2. Nonsense mutation

3. Missense mutation

Silent mutation

still codes for correct protein → little to no loss in protein structure/function

Nonsense mutation

codes for STOP sequence, UGA, UAG, UAA → early termination

Missense mutation

codes for different protein

• conservative: codes for similar functional group protein → function preserved/slightly altered

• non-conservative: codes for different functional group protein → function significantly altered

Example of point mutation

Sickle Cell Anemia

• single substitution: T replaced w/ A

• results in Valine protein = sickle cell hemoglobin (should be Glutamic acid)

  • non conservative missense mutation

types of insertions & deletions: Chromosomal mutations

1. frameshift mutation

2. Insertion/deletion of 3 nucleotides/bases

1. frameshift mutation

• extensive missense mutations → incorrect protein

• immediate nonsense mutations → stop codon

2. Insertion/deletion of 3 nucleotides/bases

• no frameshift; extra or missing amino acid protein

example of insertion/deletion or chromosomal mutation

Cystic Fibrosis: trapped mucus in airways

• deletion in CFTR gene = non functioning CFTR channel in lungs