7b mutation

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Mutations

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7b mutation

  1. 1. Protein Synthesis and Mutation• Gene Regulation in Prokaryotes• Mutation(Permanent, heritable DNA changes) • Point mutation (base substitutions) • Missense mutation • Nonsense mutation (premature stop) • Silent mutation • Insertions/deletions • Frameshift mutation • Dramatic change in amino acids • Run-ons, premature stops (nonsense mut.)• The Creation of Mutation (mutagenesis) • Spontaneous mutation • Occurs in DNA replication (1 in 109 bp) • Chemical mutagens • Base pair changers (nitrous acid) • Base analogues (e.g.. 5 bromouracil) • Frameshift mutagens (aflatoxin, benzpyrene) • Radiation • X rays, gamma rays break DNA, bases • UV light causes knots in DNA strandProteins are made by translation of genetic instructions by a ribosome. Mutations in the genetic instructions usually changes the resultant protein with deleterious effects.
  2. 2. Genes in Prokaryotes Are Grouped Together and Regulated TogetherInducible operon of genes (normally “off”) Repressible operon of genes (normally “on”) Used in “rainy day” gene sets like for Used to regulate genes that are used all the time, lactose utilization like amino acid making genes
  3. 3. Mutation: Some Definitions• A heritable change in the genetic material• Mutations may be neutral, beneficial, or harmful• Mutagen: Agent that causes mutations• Spontaneous mutations: Occur in the absence of a mutagen
  4. 4. Mutation: Base Substitution (Point Mutations) G G C C Glu (a) Silent mutation (d) Run-on mutation
  5. 5. Regulation of Bacterial Gene Expression• Steps in Translation of mRNA • Initiation, Elongation, Termination• Mutation(Permanent, heritable DNA changes) • Point mutation (base substitutions) • Missense mutation • Nonsense mutation (premature stop) • Silent mutation • Insertions/deletions • Frameshift mutation • Dramatic change in amino acids • Run-ons, premature stops (nonsense mut.)• The Creation of Mutation (mutagenesis) • Spontaneous mutation • Occurs in DNA replication (1 in 109 bp) • Chemical mutagens • Base pair changers (nitrous acid) • Base analogues (e.g.. 5 bromouracil) • Frameshift mutagens (aflatoxin, benzpyrene) • Radiation • X rays, gamma rays break DNA, bases • UV light causes knots in DNA strandProteins are made by translation of genetic instructions by a ribosome. Mutations in the genetic instructions usually changes the resultant protein with deleterious effects.
  6. 6. Mutation: Insertions and Deletions THEBIGCATATETHERAT THEBIGCBATATETHERAT Figure 8.17a, d
  7. 7. Summary of Mutation Types Run-on mutation Stop codon lost so protein is extra long (can also produce nonsense and run-ons)
  8. 8. Protein Synthesis and Mutation• Steps in Translation of mRNA • Initiation, Elongation, Termination• Mutation(Permanent, heritable DNA changes) • Point mutation (base substitutions) • Missense mutation • Nonsense mutation (premature stop) • Silent mutation • Insertions/deletions • Frameshift mutation • Dramatic change in amino acids • Run-ons, premature stops (nonsense mut.)• The Creation of Mutation (mutagenesis) • Spontaneous mutation • Occurs in DNA replication (1 in 109 bp) • Chemical mutagens • Base pair changers (nitrous acid) • Base analogues (e.g.. 5 bromouracil) • Frameshift mutagens (aflatoxin, benzpyrene) • Radiation • X rays, gamma rays break DNA, bases • UV light causes knots in DNA strandProteins are made by translation of genetic instructions by a ribosome. Mutations in the genetic instructions usually changes the resultant protein with deleterious effects.
  9. 9. Spontaneous and Induced Mutation• Spontaneous mutation rate = 1 in 109 (a billion) replicated base pairs or 1 in 106 ( a million) replicated genes. Mistakes occur during DNA Replication just before cell division. This is natural error rate of DNA polymerase.• Mutagens increase mistakes to to 10–5 (100 thousand) or 10–3 ( a thousand) per replicated gene
  10. 10. Chemical Mutagens Base pair altering chemicals (base modifiers) deaminators like nitrous acid, nitrosoguanidine, or alkylating agents like cytoxan cytoxan Nitrous acidBase analogues “mimic” certain bases but pair with others - E.g. 5-fluorouracil, cytarabine Incorporated as a “T” Acts like a “C” cytarabine
  11. 11. Chemical Frameshift Mutagens Intercalate into DNA Carboplatin (anti-cancer drug) Benzpyrene in cigarette smoke Aflatoxin fromAspergillus fungus growing on corn Daunarubicin (anti-cancer drug) AT AT AT GC GC GC CG TA TA TA GC GC GC Bleomycin (anti-cancer drug produced by CG CG CG Streptomyces)
  12. 12. Protein Synthesis and Mutation• Steps in Translation of mRNA • Initiation, Elongation, Termination• Mutation(Permanent, heritable DNA changes) • Point mutation (base substitutions) • Missense mutation • Nonsense mutation (premature stop) • Silent mutation • Insertions/deletions • Frameshift mutation • Dramatic change in amino acids • Run-ons, premature stops (nonsense mut.)• The Creation of Mutation (mutagenesis) • Spontaneous mutation • Occurs in DNA replication (1 in 109 bp) • Chemical mutagens • Base pair changers (nitrous acid) • Base analogues (e.g.. 5 bromouracil) • Frameshift mutagens (aflatoxin, benzpyrene) • Radiation • X rays, gamma rays break DNA, bases • UV light causes knots in DNA strandProteins are made by translation of genetic instructions by a ribosome. Mutations in the genetic instructions usually changes the resultant protein with deleterious effects.
  13. 13. Mutation: Ionizing Radiation• Ionizing radiation (X rays, gamma rays, UV light) causes the formation of ions that can react with nucleotides and the deoxyribose-phosphate backbone.• Nucleotide excision repairs mutations
  14. 14. X-rays and Gamma Rays Cause Breaks in DNA
  15. 15. Ionizing Radiation: UV• UV radiation causes thymine dimers, which block replication.• Light-repair separates thymine dimers• Sometimes the “repair job” introduces the wrong nucleotide, leading to a point mutation. Figure 8.20
  16. 16. Mismatch and SOS/”Light” Repair: Error Prone RecA
  17. 17. Protein Synthesis and Mutation• Steps in Translation of mRNA • Initiation, Elongation, Termination• Mutation(Permanent, heritable DNA changes) • Point mutation (base substitutions) • Missense mutation • Nonsense mutation (premature stop) • Silent mutation • Insertions/deletions • Frameshift mutation • Dramatic change in amino acids • Run-ons, premature stops (nonsense mut.)• The Creation of Mutation (mutagenesis) • Spontaneous mutation • Occurs in DNA replication (1 in 109 bp) • Chemical mutagens • Base pair changers (nitrous acid) • Base analogues (e.g.. 5 bromouracil) • Frameshift mutagens (aflatoxin, benzpyrene) • Radiation • X rays, gamma rays break DNA, bases • UV light causes knots in DNA strandProteins are made by translation of genetic instructions by a ribosome. Mutations in the genetic instructions usually changes the resultant protein with deleterious effects.

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