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Mutations

Mutations. What happens if there is a mistake in DNA? What causes the change in DNA? How does that mistake affect an organism?. Interest Grabber. Section 12-4. Determining the Sequence of a Gene

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Mutations

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  1. Mutations What happens if there is a mistake in DNA? What causes the change in DNA? How does that mistake affect an organism?

  2. Interest Grabber Section 12-4 • Determining the Sequence of a Gene • DNA contains the code of instructions for cells. Sometimes, an error occurs when the code is copied. Such errors are called mutations. • Mutations may result in disorders, diseases, changes in appearance, or they may have no effect at all.

  3. Mutations • Changes in the DNA sequence that affect genetic information • Mistakes occur every now and then • There are many different types of mistakes: • Inserting the wrong base • Deleting a base • Skipping a base • Etc…

  4. Types of mutations • Gene mutations result from changes in a single gene • Chromosomal mutations involve changes in whole chromosomes

  5. Gene mutations • Point mutations: mutations that affect one nucleotide occurring at a single point in the DNA sequence • Substituting one nucleotide for another generally change one of the amino acids in a protein In sickle celled anemia a different protein is made In cystic fibrosis a stop codon is made

  6. Substitution example (Point mutation) For example: DNA: TAC-GCA-TGG-AAT mRNA: AUG-CGU-ACC-UUA amino acids: Met – Arg – Thr – Leu The 2nd “C” in the DNA is substituted by a “T” DNA: TAC-GTA-TGG-AAT mRNA: AUG-CAU-ACC-UUA amino acids: Met – His – Thr – Leu

  7. Gene mutations • Frame-shift mutations: mutations that add or remove a nucleotide, shifting the nucleotides (“reading frame”) to make different codons • Adding/removing one nucleotide affects every amino acid following the insertion or deletion severely altering the performance of the protein • For example: THE FAT CAT ATE THE RAT • Deletion of H:TEF ATC ATA TET HER AT Nucleotides are added, so different proteins are made, decreasing strength of muscles

  8. Insertion Example(Frame-shift mutation) For example: DNA: TAC-GCA-TGG-AAT mRNA: AUG-CGU-ACC-UUA amino acids: Met – Arg – Thr – Leu A “T” is added between the 1st A & C DNA: TAT-CGC-ATG-GAA-T mRNA: AUA-GCG-UAC-CUU-A amino acids: Ile– Ala – Tyr – Leu

  9. Chromosomal mutations • There are four chromosomal mutations: • Deletion: loss of all or part of a chromosome • Duplication: segment of a chromosome is repeated • Inversion: orient part of chromosome in reverse direction • Translocation: part of one chromosome breaks off and attaches to another, non-homologous, chromosome.

  10. Please draw these chromosomal mutations Deletion Duplication Inversion Translocation

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