Mutations and gene regulationlecture 12-4, 12-5

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12-4 Mutations

What are Mutations? Changes in the genetic material.

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Kinds of Mutations

• Substitutions usually affect no more than a single amino acid.

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Insertion

• An extra base is inserted into a base sequence.

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Deletion• A single base is deleted and the reading frame

is shifted.

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Chromosome Mutations: changes to the whole chromosome

• Deletions

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• Inversions reverse the direction of parts of chromosomes.

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• Translocations : part of one chromosome breaks off and attaches to another.

Significance

• Many mutations are neutral.

• Some can cause genetic diseases.

• Some can be helpful, like resistance to HIV, or polyploidy in plants.

How does DNA make different cells?

• All cells have a full set of DNA

• Not all the DNA is expressed in each one

• Promoters and repressors allow only certain genes to be expressed (make protein)

Nerve, cardiac, muscle, white blood cells

Gene expression

• Cells turn their genes on and off as needed.• Repressor proteins stop expression of a gene.• The gene is activated when the repressor is

removed.

The gene that breaks down lactose is repressed

• When lactose is added, it binds to the repressor protein.

When lactose binds to the repressor, it movesaway, allowing the protein to be made.

Hox genes

• Hox genes control the basic structure of many animals.

• They are inherited from the genes of our common ancestors.