Bacterial Genetics Supplemental instruction Designed by Pyeongsug Kim ©2010 Fall 2010 For Dr. Wright’s Bio 7/27 Class Picture from

Designed by Pyeongsug Kim, ©2009 Picture from Dr. Wright’s Bio27 Slides ___________: Duplication of a DNA molecule.; its encoded information can be passed on to future generation. ___________: synthesis of RNA from a DNA template. ___________: formation of a protein (amino acid sequence) from RNA sequence. Transcription Translation Replication

Designed by Pyeongsug Kim, ©2009 Bacterial genome Picture from Many bacteria have….. Single, circular DNA Plasmids Small, circular double-stranded DNA Can encode a variety of genes not essential bacterial genes may give new properties conjugation Operons a group of genes expressed together a functioning unit of DNA sequence -promoter -operator -structural genes

Designed by Pyeongsug Kim, ©2009 Repressor binds to operator  blocks transcription. Corepressor binds to the repressor  alters its shape  enabling the repressor to bind to the operator.  Transcription OFF! Inducer binds to the repressor  alters its shape  preventing the repressor to bind to the operator.  Transcription ON! Picture from Dr. Wright’s Bio27 Slides

Designed by Pyeongsug Kim, ©2009 Lactose operon (lac operon) -inducible operon -Lactose as a inducer. -Genes are expressed (turn on) only if lactose (inducer) is present. If Lactose present genes are expressed.  transcription on! If Lactose is absent genes are not expressed.  transcription off!

Designed by Pyeongsug Kim, ©2009 Tryptophan operon (trp operon) -Repressible operon -Tryptophan as a corepressor. -Genes are not expressed (turn off) if tryptophan (corepressor) is present. Picture from

Mutations (rare) -One or more amino acid is changed as a result.  Bases (nucleotides) are changed or substituded -may be induced by radiation or chemical(mutanogens). -Mutations can have a significant effect on genetic diversity. -New traits acquisition of resistance can be transmitted to other microbes. -Antimicrobial (Drug) Resistance Designed by Pyeongsug Kim, ©2009 Picture from Bacteria proliferate rapidly by binary fission.

Designed by Pyeongsug Kim, ©2009 Mutagens -Chemicals or radiation that changes the genetic material  induced mutation Base analogs -incorporated into DNA  replace normal base with base analog(similar base)  Base substitution Intercalating agents -inserted (intercalated) b/w base pairs  replace normal base with base analog -Frame shift mutation  addition or subtraction of base pairs Transposons -Random insertion into any gene.  The gene inactivated. -Common in lab.

Mutagens (cont’d) -Radiation UV ~base subsitution X Rays ~deletion of base Designed by Pyeongsug Kim, ©2009 Picture from

Ames test -uses bacteria to test chemicals…. “Is this chemical mutagen? Carcinogens?” -more rapid and inexpensive -More colonies than control plate (than normal)  “This is mutagen!” Designed by Pyeongsug Kim, ©2009 Picture from Dr. Wright’s Bio27 Slides

Gene transmission in bacteria Designed by Pyeongsug Kim, ©2009 transformation, transduction and conjugation ____________ - uptake of “naked” DNA ____________ - by bacteriophages ____________ - bacterial cells come in direct contact with each other. - Plasmid is often transferred Transformation Transduction Conjugation Picture from

Designed by Pyeongsug Kim, ©2009 Transduction

Designed by Pyeongsug Kim, ©2009 Picture from Dr. Wright’s Bio27 Slides A B C Transduction Conjugation A: B: C:

B Transformation Conjugation Transduction Designed by Pyeongsug Kim, ©2009 Picture from A A: B: C: C

Designed by Pyeongsug Kim, ©2009 Picture from Transformation, Transduction and Conjugation Which one can be performed in Laboratory? ALL Which one can cause antibiotic resistace? ALL

Picture from Transduction