gene regulation in prokaryotes mutation(permanent, heritable dna changes) point mutation (base...

17
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 10 9 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

Upload: oswin-heath

Post on 16-Jan-2016

229 views

Category:

Documents


0 download

TRANSCRIPT

Page 1: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

• 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

Page 2: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

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

Page 3: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

• 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

Page 4: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

Mutation: Base Substitution (Point Mutations)

G

C

Glu

(d) Run-on mutation

G

C

(a) Silent mutation

Page 5: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

• 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

Page 6: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

Mutation: Insertions and Deletions

Figure 8.17a, d

THEBIGCATATETHERAT

THEBIGCBATATETHERAT

Page 7: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

Run-on mutationStop codon lost so

protein is extra long

(can also produce nonsense and run-ons)

Summary of Mutation Types

Page 8: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

• 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

Page 9: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

• 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

Page 10: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

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

Page 11: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

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)

Page 12: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

• 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

Page 13: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

• 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

Page 14: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

X-rays and Gamma Rays Cause Breaks in DNA

Page 15: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

• 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

Page 16: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

Mismatch and SOS/”Light” Repair: Error Prone

RecA

Page 17: Gene Regulation in Prokaryotes Mutation(Permanent, heritable DNA changes) Point mutation (base substitutions) Missense mutation Nonsense mutation (premature

• 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