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Mutations MUTATIONS Mutations • Mutation A change in

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Mutations MUTATIONS Mutations • Mutation A change in Powered By Docstoc
					MUTATIONS
                   Mutations
• Mutation: A change in the DNA sequence (gene),
  that also changes the protein it codes for.

• In Sex Cells: can produce new traits or cause
  functional problems in cells… may cause fatality
   – Can have positive effects (rare) which lead to
     evolution

• In Body Cells: impairs the function of the cell;
  mutation passed on to daughter cells, NOT offspring!
   – Mutations in genes that control cell division =
     cancer!!!
          Point Mutations
• Point Mutation: A change in a single
  nitrogen base in DNA

• Can change one amino acid, which
  changes the entire structure of a protein

• Can create a stop codon in the wrong place
• Example:
  – THE DOG BIT THE CAT
  – THE DOG BIT THE CAR
Point Mutations
        Frameshift Mutation
• When a single base is added or deleted from
  DNA

• This shifts the reading of codons by one base

• Causes a change in nearly ALL the amino acids
  following the mutation

• Example:
  – THE DOG BIT THE CAT
  – THE DO_ BIT THE CAT (Deletion of G)
  – THE DOB ITT HEC AT
Frameshift Mutation
   Chromosomal Mutations
• Mutation that occurs at the chromosome level,
  resulting in changes in gene distribution to sex
  cells (gametes) during meiosis.

• Caused when parts of chromosomes break off
  and rejoin incorrectly

• Can cause there to be too many or not enough
  chromosomes in our sex cells

• 4 Types: Deletions, Insertions, Inversions,
  Translocations
Chromosomal Mutations
      Causes of Mutations
• Mutations can be caused by either
  internal factors or external environmental
  factors.

• Spontaneous mistakes can occur during
  replication, transcription, and/or
  translation causing a variety of
  mutations.

• Mutagens are factors in the external
 environment that cause changes in
 the DNA sequence.
     Causes of Mutations
–Radiation
 • High energy rays “blast” DNA apart.
   Mutations occur as these sections
   reform.
 • X-rays
 • UV rays
 • Nuclear radiation
       Causes of Mutations
– Chemicals
   • Asbestos- used in houses because is
     resistant to heat, causes mesothelioma,
     cancer in the lining of the lungs.

  • Formaldehyde- shown to cause lung cancer
    in rats and possibly in humans.
         Repair of Mutations
• Enzymes act as editors to proofread the DNA
  and make corrections.
• Limited exposure to external mutagens is the
  best protection against mutations

              Base-pairing
              Mistake              Another enzyme
                                   fills in the missing
                                   nucleotides.
              Enzyme cuts out
              the damaged
              DNA segment

                                   The new nucleotides
                                   are sealed in,
                                   completing the DNA
                                   strand.

				
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