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Mutations

Biology 12. Mutations. JOKE OF THE DAY:. What Are Mutations?. Changes in the nucleotide sequence of DNA May occur in somatic cells (aren’t passed to offspring) May occur in gametes (eggs & sperm) and be passed to offspring

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Mutations

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  1. Biology 12 Mutations

  2. JOKE OF THE DAY:

  3. What Are Mutations? • Changes in the nucleotide sequence of DNA • May occur in somatic cells (aren’t passed to offspring) • May occur in gametes (eggs & sperm) and be passed to offspring • The errors may occur during transcription to mRNA sequence or during DNA replication

  4. Causes: • Exposure to mutagenic agents can increase the chance of mutations occurring • UV (ultraviolet) radiation • Chemicals • X rays

  5. Chromosomal • Affects multiple genes • May affect genes on separate chromosomes • Point Mutation (gene mutation) • Copying errors • Only one or a few nucleotides are affected Types of Mutations

  6. Deletion Insertion Substitution Types of Point Mutations:

  7. A nucleotide is left out • This shifts the reading of the DNA over one resulting in an incorrect protein AAGCCC GGC AAA AA CCC GGC AAA ← shifts over Result: AAC CCG GCA AA 1. Deletion

  8. 1. Deletion cont’d mRNA Protein Met Lys Phe Gly Ala Nucleotide deletion Met Lys Leu Ala His

  9. An extra nucleotide is added • This shifts the reading of the DNA over one resulting in an incorrect protein AAG CCC GGC AAA AAG ACC CGG CAA A 2. Insertion

  10. 2. Insertion cont’d

  11. Inserting or deleting one or more nucleotides changes the “reading frame” like changing a sentence • Proteins built incorrectly • Silly example: • Original: • The fat cat ate the wee rat. • Frame Shift (“a” added): • The fat caatet hew eer at. Frame shift:

  12. One nucleotide replaces another and creates a new codon • Only affects one amino acid in the protein • Possibly could be a silent mutation AAG CCC GGC AAA AAG ACC GGC AAA 3. Substitution

  13. 3. Substitution cont’d mRNA Protein Met Lys Phe Gly Ala Base substitution Met Lys Phe Ser Ala

  14. Amino acid is not changed DNA RNA Amino Acid CTA = GAU = Asp CTG= GAC = Asp Silent Mutation

  15. mRNA = GCU ACU CAA UUC • Translate the mRNA above into amino acids. • Translate each mutated mRNA below. • GCU ACU CGA UUC • GCU ACG CAA UUC • GCU ACU UCA AUU C • What was the result of each mutation? • Which would be most harmful? Try it :

  16. Page 263 • Questions: 2, 6, 7 • Page 274 • Questions: 10 (a, b) Try it :

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