1. Genes and Gene Mutations

3. Gene: a sequence of DNA bases that code for a product, usually a protein. Gene mutation: a change in the sequence of bases within a gene. Mutations can be beneficial – May enable an organism to handle stress in the environment. Can lead to malfunctioning proteins in cells.

4. Mutations may occur in… Gametes – May be passed to offspring Somatic cells – Not passed to offspring – May result in cancer

5. Three Causes of Mutations Errors in replication – Rare – DNA polymerase “proofreads” the new strand against the old strand – Usually, mismatched pairs are replaced with the correct nucleotide.

6. Three Causes of Mutations Mutagens – Environmental influences – Radiation (radioactive elements, X rays, UV light), chemicals (cigarettes, pesticides) – Rate is low because DNA repair enzymes monitor and repair irregularities. – Ex. Cancer

7. Three Causes of Mutations Transposons – Specific DNA sequences that move within and between chromosomes. – “Jumping genes” – Movement to a new location can alter neighbouring genes by increasing or decreasing their expression. – Ex. Hemophilia: the ability of blood to clot is reduced. The protein to clot blood isn’t made properly.

8. Types of Mutations Frameshift mutations – One or more nucleotides are inserted or deleted – The polypeptide codes for the wrong sequence of amino acids. THE FAT CAT ATE THE RAT THE FAT HCA TAT ETH ERA T H THE FAT CAT ATE THE RAT TEF ATC ATA TET HER AT H Ex. Tay-Sachs Disease. Several deletions and insertions lead to an early stop codon.

11. Types of Mutations Point Mutations – One nucleotide is substituted for another. THE FAT CAT ATE THE RAT THE FAT HAT ATE THE RAT

12. Types of Mutations Point Mutations Silent Mutation: There is no change if the new codon codes for the same amino acid. Ex. if GAA is changed to GAG. Both code for glutamate.

13. Types of Mutations Point Mutations Nonsense Mutation: Codon codes for a stop. Ex. Cystic fibrosis

14. Types of Mutations Point Mutations Missense Mutation: Codon codes for the wrong amino acid. Affects the shape of the protein. Ex. Sickle-Cell Anemia. Valine is added instead of glutamate.