12-4 Mutations

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12-4 Mutations
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• Mutation change in genetic material
• Gene mutation changes in a single gene
• Chromosomal mutation changes in whole
  chromosomes (affects many genes)

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Gene Mutations

• Point Mutations Changes in one or a few
  nucleotides
• Include substitutions, insertions, and deletions

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Types of Point Mutations

• Substitutions one base is changed to another
• Usually affects a single amino acid
• Insertions one base is inserted
• Deletions one base is deleted
• More dramatic changes
• Cause frameshift mutations
• Changes all amino acids after the
• point of change

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Frameshift Mutations

• mutation that shifts the reading frame of the
  genetic message by inserting or deleting a
  nucleotide
• May change every amino acid after that point
• Frameshift mutations can alter a protein so much
  that it is unable to perform its normal functions.

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Chromosomal Mutations

• Changes in the number or structure of chromosomes
• May even change the number of copies of some genes

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5 Types of Chromosomal Mutations

• Insertions addition of part of a chromosome
• Deletions loss of all or part of a chromosome
• Duplications extra copies of parts of a
  chromosomes
• Inversions reverse direction of parts of a
  chromosomes
• Translocations part of one chromosome breaks
  off and attaches to another

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Chromosomal Mutations
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Significance of Mutations

• Most have little effect
• Most mutations occur in portions of the DNA that
  is not currently being used.
• Dramatic changes usually harmful
• Producing defective proteins that dont do their
  job
• Mutations source of genetic variability!
• Can be very good! Useful!

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Polydactyly
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12-5 Gene Regulation

• A typical gene includes start and stop signals,
  with the nucleotides to be translated in between.
  
• Regulatory Sites determine is gene is on or off.

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Lac Repressor in E. coli

• Prokaryotic cells
• Cells turn genes on and off as needed

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Eukaryotic Gene Regulation

• Similar but more complex than prokaryotes
• Many eukaryotic genes include a sequence called
  the TATA box that may help position RNA
  polymerase.

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• Enhancer sequences in DNA Protein binding area
  that can
• enhance transcription by opening up tightly
  packed chromatin
• attract RNA polymerase
• block access to genes
• More complex because of cell specialization
• Not all proteins are needed in every cell