mutations and gene regulation lecture 12-4, 12-5
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Mutations and gene regulationlecture 12-4, 12-5
Copyright Pearson Prentice Hall
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.
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