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Mutations

Mutations. Mutations. Defined : a change in an organism’s DNA Where: DNA or Chromosomes When: During replication, Synapses, or Crossing-Over Mutations can affect a single gene or an entire chromosome: Some gene mutations change phenotype (physical characteristics)

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Mutations

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  1. Mutations

  2. Mutations • Defined: a change in an organism’s DNA • Where: DNA or Chromosomes • When: During replication, Synapses, or Crossing-Over • Mutations can affect a single gene or an entire chromosome: • Some gene mutations change phenotype (physical characteristics) • Example: Can cause a premature stop codon • Some gene mutations don’t change phenotype. • Example: Could be silent or occur in a non-coding region

  3. Defined: one nucleotide is substituted for another Often repaired by DNA Polymerase (spellchecker) enzyme May lead to amino acid change (see animation) May not lead to any change (Silent Mutation) Ex: DNA “CCC” is mutated into “CCG” Same amino acid is created (glycine) Gene: Point Mutations T A C A G T G G T C A A A DNA U G U C A C A C A G U U U mRNA cysteine glutamine histidine glutamine phenylalanine Amino acids

  4. Gene: Frame Shift Mutation (deletion) C A C A G T G G T C A A A DNA Defined: Insertion/deletion of a nucleotide • Entire sequence of DNA/RNA after the mutation is shifted (see animation) • Much more serious to the structure/function of the final protein • mRNA sequence may have early or late “stop codons” G U G U C A C C A G U U U mRNA cysteine histidine glutamine phenylalanine Amino acids histidine serine leucine

  5. Gene: Frame Shift Mutation (insertion) C A C A G T G G T C A A A DNA U G U C A C C A G U U U G mRNA histidine glutamine phenylalanine cysteine Amino acids glutamine proline valine Defined: Insertion/deletion of a nucleotide • Entire sequence of DNA/RNA after the mutation is shifted (see animation) • Much more serious to the structure/function of the final protein • mRNA sequence may have early or late “stop codons”

  6. Impact on Offspring • Somatic cell mutations • Affect only the individual • Not passed on to future generations • Ex: Muscle cell mutation • Germ cell mutations • May be passed to future generations (either harmful or beneficial) • Ex: Sperm cell mutation • Natural selection often removes mutant alleles from a population when they are less adaptive.

  7. Mutation Causes • Mutagen: agents in the environment that can change DNA • Speed up replication process • Break apart nucleotides • Ex: UV sunlight breaks hydrogen bond between thymine (T) and adenine (A)

  8. REview • What is a mutagen and how do they cause problems? • How are proteins affected if the DNA code is mutated? Example: ATTCGAGG is mutated to ATTCGTGG • What is the difference between a point mutation and frame shift mutations? • When are mutations passed on to future generations? • Are all mutations considered bad/dangerous? Explain.

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