1. Genes & Mutations
Miss Richardson
SBI4U

2. 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

3. 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

4. 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

5. 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

6. 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

7. 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