Genetic Mutations

• Factors Causing Mutations

  1. Mutations occur in the DNA sequence due to mistakes during DNA replication or environmental factors like UV light and cigarette smoke

  2. Factors causing mutations are called mutagens, which can be toxic chemicals and harmful radiation
• Mutagens


  • Toxic chemicals
  • Harmful radiation
• Mistakes during DNA Replication

  Can lead to mutations in the DNA sequence
• Mistakes during Mitosis


  Can lead to the production of daughter cells with too many or too few chromosomes, known as aneuploidy
• Aneuploidies that arise due to mistakes in meiosis or during early embryonic development are lethal, except for trisomy 21 in humans
• Mistakes during Meiosis


  The most common error is nondisjunction, where chromatids fail to separate during anaphase I or II, leading to imbalances in the number of chromosomes in daughter cells
• Only mutations in sex cells or reproductive cells pass on to offspring
• Mutations can affect the reproductive cells of an organism by changing the sequence of nucleotides within a gene in a sperm or an egg cell
• Mutations can alter the genetic makeup of an organism by changing the sequence of nucleotides within a gene in a sperm or an egg cell
• Mutations can occur in two different cells: Reproductive Cells and Body Cells
• If a mutated gene in an egg cell is fertilized, it becomes part of the genetic makeup of the offspring
• Types of Mutation


  • Missense Mutation
  • Nonsense Mutation
  • Silent Mutation
  • Insertion or Deletion Mutation
  • Duplication Mutation
  • Frameshift Mutation
  • Repeat Expansion Mutation
• Missense Mutation results in a change in one DNA base pair that substitutes one amino acid for another in the protein made by a gene
• Nonsense Mutation results in a premature signal to stop building a protein, leading to a shortened protein that may function improperly or not at all
• Silent Mutation does not affect the structure or function of the protein as there is no effect on the amino acid sequence
• Insertion or Deletion Mutation may result in a gene that does not function properly due to changes in the DNA bases
• Duplication Mutation involves abnormally copying a piece of DNA one or more times, potentially altering the function of the resulting protein
• Frameshift Mutation occurs when the addition or loss of DNA bases changes a gene's reading frame, affecting the code for amino acids
• Repeat Expansion Mutation increases the number of times a short DNA sequence is repeated, potentially affecting the function of the resulting protein
• Insertions, deletions, and duplications can all be frameshift mutations