Genetic Mutations Detailed Notes

Genetic Mutations

Types of Gene Mutations

• Normal DNA Sequence:TAT CAT CCT AAG GTA
  • Amino Acids: Tyr His Pro Lys Val

Examples of Mutations:

• Substitution Mutation:

  • Changed Sequence:
    TAT CAT CGT AAG GTA
  • Amino Acids: Tyr His Arg Lys Val

• Insertion Mutation:

  • Changed Sequence:
    TAT CAT CGC TAA GGT A
  • Amino Acids: Tyr His Arg Stop Gly

• Deletion Mutation:

  • Changed Sequence:
    TAT C_C CTA AGG TA
  • Amino Acids: Tyr Leu Leu Arg

Mutations and Their Effects on Proteins

• General Info:

  • Mutations occur during DNA replication.

• Classification:

  • Point Mutations:
  • Definition: One nucleotide is replaced by another.
  • Frameshift Mutations:
  • Definition: Insertion or deletion of a nucleotide changes the reading frame.

Point Mutations

• Types of Point Mutations:

  • Silent Mutation: No change in protein.
  • Nonsense Mutation: Leads to a premature stop codon.
  • Missense Mutation: A different amino acid is produced.
  • Subtypes:
    • Conservative: Similar properties of amino acids.
    • Non-conservative: Different properties of amino acids.

• Examples:

  • DNA Level:
  • TTC vs TTT
  • mRNA Level:
  • AAG vs AAA
  • Protein Level:
  • Lys vs Lys

Frameshift Mutations

• Normal Sequence:

  • e.g. ATG CAT TGC

• Example of Insertion:

  • Original Sequence: ATTGCATTGC
  • Change: Reading frame altered due to insertion.

Chromosome Structure Changes

• Types of Changes:
  • Deletion: Segment of a chromosome breaks off.
  • Duplication: A segment occurs more than once.
  • Inversion: A segment is reversed 180 degrees.
  • Translocation: A segment moves to a non-homologous chromosome.

Examples:

1. Deletion:

   • Original: A B C D E F G H
   • After Deletion: A B C E F G H

2. Duplication:

   • Original: A B C D E F G H
   • After Duplication: A B C B C D E F G H

3. Inversion:

   • Original: A B C D E F G H
   • After Inversion: A D C B E F G H

4. Translocation:

   • Original: A B C D E F G H
   • After Translocation:
     A B P Q R
M N O