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Mutations

Mutations. Defined : one nucleotide is substituted for another Often repaired by spellchecker enzyme May lead to amino acid change See animation May not lead to any change (Silent Mutation) Ex: DNA “CCC” is mutated into “CC G ” Same amino acid is created (glycine). Gene: Point Mutations.

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Mutations

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  1. Mutations

  2. Defined: one nucleotide is substituted for another Often repaired by 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

  3. Gene: Frame Shift Mutation C A C A G T T 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 an early “stop codon” • mRNA sequence may have a late “stop codon” G U G U C A A C A G U U U mRNA cysteine glutamine glutamine phenylalanine Amino acids histidine serine leucine

  4. Gene: Frame Shift Mutation 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

  5. Chromosome Mutations • Translocation: Chromosome segments combine with nonhomologous chromosome • Many genes wind up on entirely different chromosomes • Gene cut apart • ½ on chr #5, ½ on chr #8

  6. This is still Down’s Syndrome

  7. Impact on Offspring • Somatic cell mutations • Affect only the individual • Not passed on to future generations • Ex: Muscle cell mutation • Germ cell mutations • Germ cells = the diploid cells that undergo meiosis to make sperm & egg • May be passed to future generations

  8. 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)

  9. Review • How are proteins affected if the DNA code is mutated? Example: ATTCGAGG is mutated to ATTCGTGG • What is the difference between point mutations, frame shift mutations, and translocation mutations? • When are mutations passed on to future generations? • What are germ cells? • What is a mutagen and how do they cause problems?

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