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Mutations

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

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  1. Mutations What happens when we change DNA?

  2. Mutations • What do you think a mutation is? • What happens to you during a mutation?

  3. Mutations • Mutations are ANY change in an organism’s DNA. • Mutations usually happen during if a mistake is made during replication (S phase).

  4. 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.

  5. 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

  6. 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!

  7. 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

  8. 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.

  9. 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!

  10. 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.

  11. 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.

  12. mutations • Now we will look at chrmosomal mutations. • Mutations that affect ONLY ONE chrmosome: • Deletion • Duplication • Inversion

  13. mutations • Now we will look at chrmosomal mutations. • Mutations that affect TWO chrmosomes: • Insertion • Translocation

  14. 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?

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