Mutations

Unit 4Chapter 12-4

Learning goals

• 1. Explain what a mutation is and how it can affect an organism.

• 2. Give the two types of cells where mutations can occur.

• 3. Describe the two types of gene mutations and give examples of each.

Mutation

• Mutation: permanent change in the DNA base sequences.

• Mutations can be good (rarely!) but usually are bad– 1. Good: make new traits– 2. Bad: change a protein structure

or gene activity

Where Mutations Occur

– Mutations in regular body cells•1. Occurs during mitosis•2. Affects the person, not the offspring•3. Affects the function of the cell

– This may cause cancer

– Mutations in making sex cells, (gametes = sperm or eggs)•1. Affects the offspring

not the person.•2. Usually is a disease.

– Ex. Tay Sachs disease, sickle-cell anemia, muscular dystrophy

Types of Mutations

• Gene Mutations: A change in the DNA sequence of a gene (2 types)– 1. Point Mutations: a change in a single base

pair in DNA • May cause change in one single amino acid or causes

no change at all. – NORMAL DNA

» DNA: TAC GCA TGG AAT» mRNA: AUG CGU ACC UUA» A.A.: Met-----ArgArg-----Thr-----

Leu– MUTATION

» DNA: TAC GTA TGG AAT» mRNA: AUG CAU ACC UUA» A.A.: Met-----HisHis-----Thr-----Leu

– 2. Frameshift Mutations: mutations that cause a change in the entire amino acid sequence following the mutation.

• Results from a Deletion or Insertion: when a single nucleotide is removed or added.

– EX: The fat cat ate the rat.» The atc ata tet her at

• Major effects! Can make protein useless.

• Chromosomal Mutations: Changes in number or structure of chromosomes.– 1. Deletion or duplication of a piece of

chromosome.– 2. Inversion: a piece of the chromosome

will detach and reattach in reverse order.– 3. Translocation: a piece of a chromosome

will break off and reattach to an entirely different chromosome.

Learning goals

• 1. Explain what a mutation is and how it can affect an organism.

• 2. Give the two types of cells where mutations can occur.

• 3. Describe the two types of gene mutations and give examples of each.