Central Dogma of Molecular Biology Genetic information flows

Central Dogma of Molecular Biology Genetic information flows in one direction – from DNA to RNA to proteins.

Bellringer What do these words mean to you? Write a short 2 word definition for each • • 1. Mutation 2. Duplication 3. Deletion 4. Insertion 5. Translocation 6. Inversion 7. Substitution

KEY CONCEPT Mutations are changes in DNA that can affect phenotype

What are Mutations? (video link)

Mutations are changes to DNA that may be • Harmful • Helpful • Have no effect.

When Mutations Occur 1. Errors can occur during: DNA Replication Protein Synthesis Meiosis .

Causes of Mutations 2. Mutagens – Environmental factors that cause changes in DNA Examples: - Radiation - Chemicals in environment

The effect mutations have on an organism’s physical characteristics depends on: 1. The number and type of genes involved 2. Type of cell the mutation occurs in – somatic or sex

Mutations in Somatic Cells: • Affect only the organism they occur in. • Cannot be passed to offspring.

Mutations in Sex (Germ) cells: • May be passed to offspring

Two Categories of Mutations: 1. Single Gene – affects one gene – usually caused by an error in DNA replication 2. Chromosomal – affects chromosomes – usually error in meiosis. Usually more harmful since many genes are affected.

Types of Chromosomal Mutations • • • Translocation Duplication Nondisjunction Deletion Inversion

• TRANSLOCATION (“transfer location”) • Piece of one chromosome breaks off and moves to a nonhomologous chromosomes.

• DUPLICATION. • Two or more copies of the same gene on a chromosome.

• NONDISJUNCTION • Homologous chromosomes don’t separate in Anaphase I • Sister chromatids don’t separate in Anaphase II

• Deletion • Section of chromosome containing one or more genes is removed

• Inversion • Section of a chromosome flips its position

Single Gene Mutations • Usually occur in DNA replication • Affect one gene and the protein made from it

Frameshift Mutation • Caused by adding or removing 1 -2 bases • Changes the reading frame • .

Type of Frameshift Mutation. Deletion - one or more bases are deleted; shifts the reading frame

Type of Frameshift Mutation Insertion - one or more bases are added; shifts the reading frame

Point Mutations • One nucleotide is replaced by another. mutated base

Types of Point Mutations Determined by their outcomes

Nonsense point mutation • Change codes for a STOP codon • Full protein not made • “NO” STOP

Missense Point Mutation * Codes for wrong amino acid * May be harmful or beneficial – depends…

Silent point mutation Does not result in a different amino acid or protein made. DNA changes but its expression (phenotype) does not.

Results of mutations may be: • Harmful – needed protein isn’t made • Have NO EFFECT – are not harmful or helpful • Beneficial are favored by natural selection – rarely occurs

Mutations increase genetic variety Natural selection favors mutations that provide survival advantage.

Laron Syndrome mutation that causes dwarfism also protects against cancer and diabetes. • ABC Evening News - Laron Syndrome

• Mutations in body cells do not affect offspring. • Only Mutations in sex cells affect offspring. • Natural selection favors mutations that provide an adaptation that has survival advantage