Genes & Mutations Miss Richardson SBI4U

Mutations occur when there is a change in the DNA gene sequence Mutations may be positive, negative or neutral Substances that cause mutations are mutagens Radiation Chemicals Viruses Mutations can also occur spontaneously Mutations

Single-Gene Mutations Point mutation: error at a single point (base pair) in the DNA Deletion Insertion Substitution/translation (can have no effect due to redundancy of genetic code) These cause a frameshift mutation Single-Gene Mutations

Single-Gene Mutations Silent mutations do not affect the function of the protein or the cell’s metabolism Missense mutations alter the amino acid produced and can be harmful Single-Gene Mutations

Chromosomal Mutations Changes in chromosomal structure: Deletion: part of chromosome is missing Duplication: part of chromosome is duplicated more than once Inversion: portion of chromosome is inverted Insertion: part of a chromosome is inserted into another chromosome Translocation: part of chromosome is translocated to end of another chromosome Chromosomal Mutations

1949 – Barbara McClintock first described transposons or ‘jumping genes’ Move from place to place and swap genetic material Excised by enzyme transposase but removal may disrupt protein synthesis Transposition

Occurs during meiosis – daughter chromosomes separate incorrectly Results in an excess or deficiency of chromosomes in the cell Eg: Down syndrome is result of an extra chromosome #21 Nondisjunction