4-4 Mutations

Intro

• Mutation: Any change in the genetic material of a cell

  • Mutations are heritable changes in genetic information (each new daughter cell will made the mutated cell will have the mutation

  • Not all mutation are inherited from parent to offspring

    • Only those taking place in cells that produce gametes (sperm and egg) will be inherited

Types of Mutations

• Gene mutations: Mutations that produce a change in a single gene

• Chromosomal mutations: Mutations that produce changes in whole chromosomes.

Gene Mutations

• Two types of gene mutations

  • Point mutations

  • Frameshift mutations

• These types of mutations generally occur during DNA replication.

  • If mistake is not caught, mutation will be passed onto every cell that develops from the original one

Point mutations

• Mutations in which a single base pair of DNA has been changed

  • Substitutions: The only point mutation and occur when on base pair is substituted for another

  • Substitutions often affect only one amino acid and sometimes have no effect at all

Frameshift Mutations

• Frameshift mutations: Mutations that shift the reading frame of the genetic message by inserting or deleting nucleotides

  • Frameshift mutations can change every amino acid that follows the point of the mutation and can alter  protein so much that it is unable to perform its normal functions

• Two types of frameshift mutations

  • Insertions

    • EX: ACG but insert a T in between two letters and now its ACTG, which is read as ACT. This could change an amino acid

  • Deletions

    • EX: ACGATT but delete the G, turning the letters into ACATT, possible changing the amino acid

• If a nucleotide is added or deleted, the bases are still read in groups of three, but now those groupings shift every codon that follows the mutation 

Effects of Mutations

• Genetic material can be altered by natural events or by artificial means

  • Many mutations are produced by eros in genetic processes including mistakes during DNA replication, mitosis or meiosis

  • Some mutations come from mutagens

    • Mutagen: A chemical or physical agent in the environment which causes mutations

      • Chemical mutagens include pesticides, tobacco smoke, environmental pollutants, and certain plant alkaloids

      • Physical mutagens include some forms of electromagnetic radiation, X-rays, gamma rays, UVA & UVB rays are all known mutagens

• Effects of mutations can vary widely. They can be:

  • Silent (or Neutral)

    • The redundancy of genetic code allows for some mutations to not change the final outcome of a protein

  • Beneficial

    • Beneficial mutations are responsible for evolution and contribute to genetic variability within a species 

  • Harmful:

    • Some of most harmful mutations are those that dramatically change protein structure or gene activity

      •  Defective proteins produced by these mutations can disrupt normal biological activities, and result in genetic disorders

      • EX: Some cancers are product of mutations that cause the uncontrolled growth of cells