gene regulation in prokaryotes mutation(permanent, heritable dna changes) point mutation (base...
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• 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 strand
Proteins are made by translation of genetic instructions by a ribosome. Mutations in the genetic instructions usually changes the resultant protein with deleterious effects.
Protein Synthesis and Mutation
Inducible operon of genes (normally “off”)Used in “rainy day” gene sets like for
lactose utilization
Repressible operon of genes (normally “on”)Used to regulate genes that are used all the time,
like amino acid making genes
Genes in Prokaryotes Are Grouped Together and Regulated Together
• 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
Mutation: Some Definitions
Mutation: Base Substitution (Point Mutations)
G
C
Glu
(d) Run-on mutation
G
C
(a) Silent 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 strand
Proteins are made by translation of genetic instructions by a ribosome. Mutations in the genetic instructions usually changes the resultant protein with deleterious effects.
Regulation of Bacterial Gene Expression
Mutation: Insertions and Deletions
Figure 8.17a, d
THEBIGCATATETHERAT
THEBIGCBATATETHERAT
Run-on mutationStop codon lost so
protein is extra long
(can also produce nonsense and run-ons)
Summary of Mutation Types
• 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 strand
Proteins are made by translation of genetic instructions by a ribosome. Mutations in the genetic instructions usually changes the resultant protein with deleterious effects.
Protein Synthesis and 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
Spontaneous and Induced Mutation
Chemical Mutagens
Base pair altering chemicals (base modifiers) deaminators like nitrous acid, nitrosoguanidine, or alkylating agents like cytoxan
Incorporated as a “T”
Base analogues “mimic” certain bases but pair with others - E.g. 5-fluorouracil, cytarabine
Acts like a “C”
cytarabine
cytoxan Nitrous acid
Chemical Frameshift Mutagens Intercalate into DNA
Aflatoxin fromAspergillus fungus growing on corn
Benzpyrene in cigarette smoke
ATGCTAGCCG
ATGC
TAGCCG
ATGCCGTAGCCG
Carboplatin (anti-cancer drug)
Daunarubicin (anti-cancer drug)
Bleomycin (anti-cancer drug produced by
Streptomyces)
• 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 strand
Proteins are made by translation of genetic instructions by a ribosome. Mutations in the genetic instructions usually changes the resultant protein with deleterious effects.
Protein Synthesis and Mutation
• 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
Mutation: Ionizing Radiation
X-rays and Gamma Rays Cause Breaks in DNA
• 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.
Ionizing Radiation: UV
Figure 8.20
Mismatch and SOS/”Light” Repair: Error Prone
RecA
• 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 strand
Proteins are made by translation of genetic instructions by a ribosome. Mutations in the genetic instructions usually changes the resultant protein with deleterious effects.
Protein Synthesis and Mutation