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Mutations. What happens when we change DNA?. Mutations. What do you think a mutation is? What happens to you during a mutation?. Mutations. Mutations are ANY change in an organism’s DNA. Mutations usually happen during if a mistake is made during replication (S phase). Mutations.

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mutations
Mutations

What happens when we change DNA?

mutations1
Mutations
  • What do you think a mutation is?
  • What happens to you during a mutation?
mutations2
Mutations
  • Mutations are ANY change in an organism’s DNA.
  • Mutations usually happen during if a mistake is made during replication (S phase).
mutations3
Mutations
  • As we’ve discussed before, your cells have many ways to prevent mutations from happening.
    • Cells use proofreading when duplicating DNA.
    • If a cell detects a mistake is made in phase G2, it self-destructs (apoptosis).
    • Your genetic code is degenerate. This means that there are multiple possibilities to make most of the amino acids.
mutations4
Mutations
  • Mutations will either change the individual DNA sequences, or an entire chromosome.
  • We will look at DNA mutations first. There are four types:
    • Substitution
    • Deletion
    • Insertion
    • Inversion
mutations5
Mutations
  • Example:

Original sequence:

THE FAT CAT ATE THE RAT.

Mutant sequence:

THE FAT HAT ATE THE RAT.

  • A substitution switches one DNA letter for another.
  • These are usually point mutations – mutations that only affect one letter!
mutations6
Mutations
  • Many point mutations are also silent mutations – they will NOT change the amino acids that are created.
  • Original sequence: AUG CCA GGG UGU

Amino acids: Met– Pro – Gly- Cys

  • Mutant sequence: AUG CCC GGU UGU

Amino acids: Met – Pro – Gly - Cys

mutations7
Mutations
  • Example:

Original sequence:

THE FAT CAT ATE THE RAT.

Mutant sequence:

THE FAT ATA TET HER AT.

  • A deletion removes one or more DNA letters at once.
  • These are always frameshift mutations – mutations that change how codons are divided.
mutations8
Mutations
  • Example:

Original sequence:

THE FAT CAT ATE THE RAT.

Mutant sequence:

THE FAT WCA TAT ETH ERA T.

  • An insertion adds one or more DNA letters at once.
  • These are also always frameshift mutations!
mutations9
Mutations
  • Example:

Original sequence:

THE FAT CAT ATE THE RAT.

Mutant sequence:

THE FAT HTE TAT ACE RAT.

  • An inversion reverses a sequence of DNA letters.
  • These usually happen during mitosis (M phase), as chromosomes line up in metaphase.
mutations10
mutations
  • Point mutation:

AUG CGA UUA → AUG CUA UUA

Met – Arg – Leu→ Met – Leu – Leu

  • Frameshift mutation:

AUG CGA UUA → AUG CGGAUU A

Met – Arg – Leu→ Met – Arg - Iso

  • Remember, point mutations leave the same number of nucleotides.
  • In contrast, frameshift mutations either add or remove nucleotides.
mutations11
mutations
  • Now we will look at chrmosomal mutations.
  • Mutations that affect ONLY ONE chrmosome:
  • Deletion
  • Duplication
  • Inversion
mutations12
mutations
  • Now we will look at chrmosomal mutations.
  • Mutations that affect TWO chrmosomes:
  • Insertion
  • Translocation
mutations non disjunction ex trisomy 21 down syndrome
Mutations: Non-DisjunctionEx: Trisomy 21 (Down Syndrome)
  • Sometimes, there is an error when egg or sperm cells divide, resulting in too many or too few chromosomes.
  • How do you think this

type of change would

impact an organism?