Chapter 12 DNA

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Chapter 12DNA RNA

• Section 12 4Mutations

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Mutations

• Key ConceptGene mutations result from changes
  in a single gene. Chromosomal mutations involve
  changes in whole chromosomes

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Gene Mutations

• Point Mutations
• Affect one nucleotide
• Occur at a single point in the gene sequence
• Three Types
• Deletion
• Insertion
• Substitution

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Point Mutations

• Frameshift Mutations
• Result From
• Insertions Deletions
• A nucleotide is added, or subtracted from the
  nucleotide sequence. This shifts the Codon
  grouping and drastically alters the amino acid
  sequence in the protein.

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Point Mutations

• Substitution
• A single nucleotide is changed in the nucleotide
  sequence.
• This may result in a change to a single amino
  acid in the protein.
• The change to a single amino acid may or may not
  alter the proteins function.

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Point Mutations - Substitution
Codon Amino Acid
UGU Original Cysteine
UGC No Change Cysteine
UGG Single AA Tryptophan
UGA Bad STOP
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Chromosomal Mutations

• Changes the number or structure of chromosomes
• May change locations of genes on chromosome or
  the number of copies of some genes

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Chromosomal Mutations

• 4 Types
• Deletion
• Duplication
• Inversion
• Translocation

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Deletion
X
Deletion Loss of all or part of a chromosome
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Duplication
Duplication Segment of chromosome is repeated
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Inversion
Inversion Chromosome or part of a chromosome is
oriented in the reverse direction
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Translocation
Translocation Part of one chromosome breaks off
and attaches to another, nonhomologous chromosome