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Mutations - PowerPoint PPT Presentation

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Mutations. Mutation. A change in the genetic material of an organism. Are mutations all bad?. Nope!. Mutation. Mutations are generally neutral or harmful to an organism In rare cases, mutations may be beneficial and provide an adaptive advantage over time. Mutations.

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Presentation Transcript
  • A change in the genetic material of an organism

Are mutations all bad?

  • Nope!
  • Mutations are generally neutral or harmful to an organism
  • In rare cases, mutations may be beneficial and provide an adaptive advantage over time

Can be put into two categories:

  • Single-gene Mutations
  • Chromosomal Mutations
single gene mutations
Single-gene Mutations

Point Mutations

  • a mutation involving a change in a single base pair within a DNA sequence
point mutations
Point mutations
  • May arise from a
    • substitution of one base pair for another
    • Deletion or insertion of one or more base pairs from the DNA sequence
types of point mutations
Types of Point Mutations
  • Silent mutations
    • No effect on aa sequence in a protein

Pg 263

types of point mutations1
Types of Point Mutations
  • Missense mutations
    • An altered codon causes a different aa to be placed in the pr-

Pg 263

types of point mutations2
Types of Point Mutations
  • Nonsense mutations
    • Shortens a protein by introducing a stop codon instead of a specific aa

Pg 263

types of point mutations3
Types of Point Mutations

Pg 262

  • Frameshift mutations
    • Changes the reading frame if one or two nucleotides are affected
chromosomal mutations
Chromosomal Mutations
  • Involve changes in chromosomes
  • May involve many genes

Types of Chromosomal Mutations

  • Deletion
  • Duplication
  • Inversion
  • Reciprocal translocation
  • A section of a chromosome is lost

Pg 263

  • A section of a chromosome is copied one or more times

Pg 263

  • (reverse orientation)
  • A chromosome is broken and re-inserted in the opposite direction

Pg 263

  • A section of one chromosome breaking and fusing to another chromosome

Pg 263

causes of mutations
Causes of Mutations

Mutations can be...

  • Spontaneous
  • Induced
causes of mutations1
Causes of Mutations

Spontaneous Mutations

  • Take place naturally in a cell as a result of normal molecular interactions
  • Can occur during DNA replication and because of DNA transposition
  • aka. jumping genes
  • A segment of DNA that can move within the genome of an organism
causes of mutations2
Causes of Mutations

Induced Mutations

  • Caused by agents outside the cell
  • Eg. Exposure to mutagens
causes of mutations3
Causes of Mutations

Types of Mutagens

  • Physical Mutagens – those that physically change the structure of DNA
  • Eg. X rays, UV rays
causes of mutations4
Causes of Mutations

Types of Mutagens

  • Chemical Mutagens - a molecule that can enter the nucleus and induce mutations by reacting chemically with DNA
  • May cause a substitution or frameshift mutation
causes of mutations5
Causes of Mutations

Types of Mutagens

  • Chemical Mutagens
  • Eg. Nitrites, gasoline fumes, chemicals in cigarette smoke
dna repair
DNA Repair

Cell have many mechanisms to repair DNA (aside from those discussed during DNA replication)

All mechanisms involve a specific set of proteins that act by recognizing and then repairing the damage.

specific repair
Specific Repair
  • Mechanisms that fix certain types of damage
  • Eg. Photorepair

Pg 265

non specific repair
Non Specific Repair
  • Can correct different forms of damage
  • Eg. Excision repair

Pg 265