Gene Mutations

Mutations only happen to DNA!!!!!! Gene Mutations A gene mutation is a change in the nucleotide sequence of a DNA molecule Some do not change the final protein produced – these are silent mutations If the final protein is affected, the mutation is said to be expressed (could be negative or positive!) Mutations only happen to DNA!!!!!!

Are mutations always bad? Mutations create genetic variation in a population. Favorable mutations give organisms an advantage over others and ensure their survival. These mutations will accumulate in a population. Less favorable mutations are removed from the gene pool through natural selection. Organisms with these mutations will not survive.

Small Scale Mutations: Gene Mutations There are three main types of gene mutations: Point Mutations Deletions (Frame shift mutations) Insertions (Frame shift mutations)

Point Mutations In a point mutation, a single nucleotide is substituted for another Original Mutation UCC CAU UAU Serine Histidine Tyrosine UCA CGU UAA Serine Arginine STOP Silent; no change Expressed; a single amino acid is changed Expressed; the protein is cut short

Examples of Point Mutations Sickle cell anemia Lactose intolerance

Frameshift mutations

Insertions Insertions occur when one or more new nucleotides are inserted into the DNA sequence. When this occurs, there is a shift in the reading sequence of DNA during protein synthesis and a completely different protein strand may be formed.

Deletions Deletions are when one or more nucleotides are removed from the DNA sequence. As with insertions, this causes a shift in the reading sequence of DNA and can produce a completely different protein strand than the original. Deletions are irreversible mutations.

Frameshift Mutations In frameshift mutations, the insertion or deletion of a nucleotide changes the entire DNA sequence Causes a drastic change in the final protein The fat cat ate the rat The fat cat aat eth era t The fat cat tet her at a

Tay-Sachs: A frameshift mutation Tay-sachs is a hereditable disorder which causes paralysis, seizures, loss of hearing and sight, and death (typically before age 5) 1 out of 250 people are a carrier (have one copy of the defective gene) The mutation is a frameshift causing a lysosome to work incorrectly Causes brain cells (neurons) to die