Genetic diversity can arise as a result of mutation

• What is a mutation

  ~An alteration to the DNA base sequence

  ~Often arise spontaneously during DNA replication
• Why might a mutation not lead to change in the amino acid sequence

  ~Genetic code is degenerate so mutation may end up coding for same amino acid as the original triplet

  ~Mutation may occur in intron
• What is a substitution mutation

  ~When a nucleotide in the DNA sequence is replaced by another

  ~This is more likely to be quiet mutation, meaning no change occurs in the amino acid sequence
• What is a deletion mutation


  ~When a nucleotide in the DNA sequence is lost

  ~This is more likely to be harmful and significant, as it leads to a frame shift which means the entire amino acid sequence will be different
• What is a mutagenic agent


  Factors that increase the rate of gene mutation
• What is a polyploidy chromosome mutation

  Where an individual has three or more sets of chromosomes instead of two
• What is chromosome non-disjunction


  When chromosomes fail to separate correctly in meiosis, resulting in gametes with one more or less chromosome than normal
• What is meiosis


  A form of cell division that produces four genetically haploid cells known as gametes
• How does meiosis differ from mitosis

  ~Meiosis produces four genetically different cells with half the number of chromosomes as the parent cells

  ~Mitosis produces two genetically identical cells with the same number of chromosomes as the parent cells
• What happens during meiosis I

  ~Homologous chromosomes pair to form bivalents

  ~Crossing over occurs at chiasmata

  ~Cells divide into two. Homologous chromosomes separate randomly. Each cell contains either maternal or paternal copy
• What happens during meiosis II

  ~Independent segregation of sister chromatids

  ~Each cell divides again, producing four haploid cells
• Give two ways meiosis produces genetic variation

  ~Crossing over during meiosis I

  ~Independent assortment of homologous chromosomes and sister chromatids

  ~Result in new combinations of alleles