CH. 11.6 Mutations in GenesObjectives: 1. Describe the

following types of mutations:

a. Base substitutionb. Base insertion or

deletion

2. Explain what can cause a mutation.

Vocabulary: MutationMutagen

Mutations

• http://www.ptbeach.com/167020813143947783/cwp/view.asp?A=3&Q=278050&C=54590

• http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mutations.html

Any change in nucleotide sequence of DNA

Effects vary:

None --> Severe

Base Substitutions

• http://www.ptbeach.com/167020813143947783/cwp/view.asp?A=3&Q=278050&C=54590• http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mutations.html

Single Base Mutation (Point Mutation)

Replacement of one base or nucleotide for another.

May or may not cause dysfunction in protein.

Base Substitutions

• http://www.ptbeach.com/167020813143947783/cwp/view.asp?A=3&Q=278050&C=54590• http://users.rcn.com/jkimball.ma.ultranet/BiologyPages/M/Mutations.html

1. Silent Mutation: Substitution does not result in a change in amino acid sequence.

(More than 1 codon for each amino acid)

Ex: GAA --> GAG still makes Glutamine

Base Substitutions

2. Missense Mutation: Substitution DOES result in an amino acid substitution.

Can have negative effects.

Sickle Cell Anemia

Sickle Cell Anemia

•Sickled R.B.C.s are angular and inflexible

•Get stuck in blood vessels and block blood flow (=PAIN).

•Less functioning RBCs = Fatigue (limits O2 delivered to cells)•http://www.nhlbi.nih.gov/health/health-topics/topics/sca/

Base Substitutions3. Nonsense Mutation: Substitution results in a STOP CODON.

•Shorter, incomplete protein

•Negative impacts vary (How much protein was translated?)

Mutations: INSERTIONS & DELETIONS“Frameshift” mutations:

Nucleotide is added or removed.•Changes codons, changes amino acid sequence

•Bigger impacts/ Different Proteins

Review Mutations

Mutagens: Cause MutationsPhysical Agents

High frequency energy

• X-rays

• UV rays

Chemical Agents

• Free-radical oxygens

• Certain chemicals (chemotherapy)

Mutations: Source of Genetic Variation

Mutations are passed to offspring.

Most lead to dysfunctional proteins.

Some are lethal.

Few - are beneficial (but important to gene pool) Variations in gene pool allow

species to survive when environmental conditions change.