SCI10 Q3 MUTATION

Mutation

  • Mutation: A change in the DNA sequence

  • Can occur due to:

    • Mistakes in DNA replication

    • Environmental factors (e.g., UV light, cigarette smoke)

  • Stages of protein synthesis:

    • Transcription: DNA to mRNA

    • Translation: mRNA to amino acids at the ribosome

  • If mRNA is copied incorrectly, this results in a mutation.

Types of Mutations

1. Point Mutations

  • Involve a single nucleotide base change: deletion, addition, or alteration

  • Types of point mutations:

    • Substitution mutation

      • Nonsense mutation: Introduces a stop codon, halting protein synthesis prematurely.

      • Missense mutation: Alters one amino acid in the protein sequence.

      • Silent mutation: Changes a base but results in the same amino acid.

2. Frameshift Mutations

  • Caused by insertion or deletion of nucleotides not in multiples of three

  • Alter the reading frame of codons, leading to significant changes in the amino acid chain

    • Can produce longer or shorter proteins

3. Chromosomal Mutations

  • Types:

    • Deletion: A base is removed from the sequence

    • Duplication: A sequence is copied excessively

    • Inversion: A segment of DNA is reversed

    • Insertion: Extra nucleotide base pairs are added

    • Translocation: Segments from two different chromosomes are exchanged

Examples of Genetic Disorders

  • Sickle Cell Anemia:

    • Caused by a single substitution mutation in the hemoglobin gene: glutamic acid replaced by valine

    • Leads to sickle-shaped red blood cells that cannot carry oxygen effectively

    • Symptoms: anemia, pain crises, frequent infections

  • Albinism:

    • Autosomal recessive disorder due to deletion of the tyrosinase gene, affecting melanin production

  • Down Syndrome (Trisomy 21):

    • Caused by translocation, leading to three copies of chromosome 21

    • Symptoms: Cognitive impairment, physical growth issues, distinct facial features

Summary

  • Mutations play a crucial role in genetic diversity and evolution but can also lead to serious disorders when they disrupt normal functions.