• 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