Mutations are changes in DNA that may or may not affect phenotype.

Some mutations affect a single gene, while others affect an entire chromosome. A mutation is a change in an organism’s DNA.

Many kinds of mutations can occur, especially during replication.

Mutagens Agents in the environment that can change DNA. UV rays X-rays Tobacco Viruses

Point Mutation (Base-pair substitution) substitutes one nucleotide for another mutated base

Frameshift Mutation inserts or deletes a nucleotide in the DNA sequence If nucleotide is inserted it can also be called Base insertion. If nucleotide is deleted it can also be called Base deletion. Cystic Fibrosis is caused by a specific deletion.

Chromosomal Mutation Chromosomal mutations affect many genes. Chromosomal mutations tend to have a big effect. Chromosomal mutations may occur through crossing over during meiosis. Two types of chromosomal mutations: Gene duplication Gene translocation

Chromosomal Mutation Gene duplication results from unequal crossing over. Chromosome has two copies of a gene or genes. Opposite of deletion.

Chromosomal Mutation Translocation results from the exchange of DNA segments between nonhomologous chromosomes. Causes rearrangements without changing the chromosomal number Causes changes to chromosome number-Downs Syndrome

Effects of Mutations Somatic Mutations Germ Mutations Mutations in body cells (not passed from parent to offspring) Usually silent but can dramatically affect an individual’s phenotype. Skin and Lung cancers Germ Mutations Mutations in gametes, sex cells (can be passed from parent to offspring) Affect the survival of an organism and change the traits of the organism’s descendants Can be beneficial or harmful Beneficial mutation may help an organism survive in a changing environment Hemophilia and Color blindness