Microbial GeneticsMicrobial Genetics

I. Structure and function of genesI. Structure and function of genes

II. Gene expression in bacteriaII. Gene expression in bacteria

III. Mutation and variationIII. Mutation and variation

IV. Horizontal gene transfer in bacteriaIV. Horizontal gene transfer in bacteria

Levels at which enzymes can be regulatedLevels at which enzymes can be regulated

In prokaryotes, expression is generally regulated at the level of _____________

In bacteria, genes are organized into operons

In bacteria, genes are organized into operons

OperonOperon -- a cluster of genes whose expression is -- a cluster of genes whose expression is controlled by a single controlled by a single operatoroperator..

OperatorOperator -- a specific region of the DNA at the -- a specific region of the DNA at the initial end of a gene or operon, where a initial end of a gene or operon, where a repressor repressor proteinprotein binds and _______________ mRNA binds and _______________ mRNA synthesis.synthesis.

Repressor proteinRepressor protein -- a regulatory protein that binds -- a regulatory protein that binds to specific sites on DNA and blocks to specific sites on DNA and blocks ______________________ .______________________ .

One method of gene regulation: enzyme _________________

One method of gene regulation: enzyme _________________

Enzyme induction, (cont.)Enzyme induction, (cont.)

The lac Operon: an example of enzyme _____________

The lac Operon: an example of enzyme _____________

http://esg-www.mit.edu:8001/bio/pge/lac.htmlhttp://esg-www.mit.edu:8001/bio/pge/lac.html

-galactosidase-galactosidase

RepressorRepressor

When lactose is unavailable, the repressor is _____________. It binds to the operator region, blocking the binding of the

___________ ______________________.

When lactose is unavailable, the repressor is _____________. It binds to the operator region, blocking the binding of the

___________ ______________________.

RepressorRepressor

No mRNA and no proteinNo mRNA and no protein

http://esg-www.mit.edu:8001/bio/pge/lac.htmlhttp://esg-www.mit.edu:8001/bio/pge/lac.html

The presence of lactose causes a conformational change in

the repressor, which renders it ________________ to bind the

__________________________

The presence of lactose causes a conformational change in

the repressor, which renders it ________________ to bind the

__________________________

http://esg-www.mit.edu:8001/bio/pge/lac.htmlhttp://esg-www.mit.edu:8001/bio/pge/lac.html

BlockedBlocked

lactoselactose

Review: lac operon without inducer (________________)

Review: lac operon without inducer (________________)

QuickTime™ and aAnimation decompressor

are needed to see this picture.

http://www.biology.arizona.edu/molecular_bio/problem_sets/mol_genetics_of_prokaryotes/02t.html?http://www.biology.arizona.edu/molecular_bio/problem_sets/mol_genetics_of_prokaryotes/02t.html?

Review: lac operon with inducer (lactose)

Review: lac operon with inducer (lactose)

http://www.biology.arizona.edu/molecular_bio/problem_sets/mol_genetics_of_prokaryotes/02t.html?http://www.biology.arizona.edu/molecular_bio/problem_sets/mol_genetics_of_prokaryotes/02t.html?

Text, Fig. 9.21Text, Fig. 9.21

Another method of gene regulation: enzyme ________________

Another method of gene regulation: enzyme ________________

Enzyme repression (cont.)Enzyme repression (cont.)

An example of enzyme repression: the ________________ operon

An example of enzyme repression: the ________________ operon

Review: enzyme inductionReview: enzyme induction

Enzyme induction, (cont.)Enzyme induction, (cont.)

Review: enzyme repressionReview: enzyme repression

Enzyme repression (cont.)Enzyme repression (cont.)

MutationMutation

Any permanent, _______________ change in Any permanent, _______________ change in the genetic information of a cell.the genetic information of a cell.

Types:Types: Point mutationsPoint mutations -- substitution, insertion, or -- substitution, insertion, or

deletion of _______________ or a few basesdeletion of _______________ or a few bases Large insertions or ________________Large insertions or ________________

Point mutations -- effects of substitution

Point mutations -- effects of substitution

Point mutations (cont.) -- insertions and

deletions result in _________________ shifts

Point mutations (cont.) -- insertions and

deletions result in _________________ shifts

Insertions or deletions of large segments of DNA can _________________ a gene (depending on where

the insertion lands)

Insertions or deletions of large segments of DNA can _________________ a gene (depending on where

the insertion lands)

Gene AGene A

Transposable Elements: “_______________ genes”Transposable Elements: “_______________ genes”

Palindromes: Go hang a salami, I'm a lasagna hogPalindromes: Go hang a salami, I'm a lasagna hog

C A T G C C G A C G T C T A C T G A A C G T C A G T C CC A T G C C G A C G T C T A C T G A A C G T C A G T C C

G T A C G G C T G C A G A T G A C T T G C A G T C A G GG T A C G G C T G C A G A T G A C T T G C A G T C A G G

G A C G TG A C G T

T G C A GT G C A GA C G T CA C G T C

C T G C AC T G C A

Transposable elementTransposable element

A man, a plan, a caret, a ban, a myriad, a sum, a lac, a liar, a hoop, a pint, a catalpa, a gas, an oil, a bird, a A man, a plan, a caret, a ban, a myriad, a sum, a lac, a liar, a hoop, a pint, a catalpa, a gas, an oil, a bird, a yell, a vat, a caw, a pax, a wag,a tax, a nay, a ram, a cap, a yam, a gay, a tsar, a wall, a car, a luger, a ward, yell, a vat, a caw, a pax, a wag,a tax, a nay, a ram, a cap, a yam, a gay, a tsar, a wall, a car, a luger, a ward,

a bin, a woman, a vassal, a wolf, a tuna, a nit, a pall, a fret, awatt, a bay, a daub, a tan, a cab, a datum, a a bin, a woman, a vassal, a wolf, a tuna, a nit, a pall, a fret, awatt, a bay, a daub, a tan, a cab, a datum, a gall, a hat, a fag, a zap, a say, a jaw, a lay, a wet, a gallop, a tug, a trot, a trap, a tram, a torr, acaper, a top, a gall, a hat, a fag, a zap, a say, a jaw, a lay, a wet, a gallop, a tug, a trot, a trap, a tram, a torr, acaper, a top, a tonk, a toll, a ball, a fair, a sax, a minim, a tenor, a bass, a passer, a capital, a rut, an amen, a ted, a cabal, a tonk, a toll, a ball, a fair, a sax, a minim, a tenor, a bass, a passer, a capital, a rut, an amen, a ted, a cabal, a

tang, a sun, anass, a maw, a sag, a jam, a dam, a sub, a salt, an axon, a sail, an ad, a wadi, a radian, a tang, a sun, anass, a maw, a sag, a jam, a dam, a sub, a salt, an axon, a sail, an ad, a wadi, a radian, a room, a rood, a rip, a tad, a pariah, a revel, a reel, areed, a pool, a plug, a pin, a peek, a parabola, a dog, a room, a rood, a rip, a tad, a pariah, a revel, a reel, areed, a pool, a plug, a pin, a peek, a parabola, a dog, a pat, a cud, a nu, a fan, a pal, a rum, a nod, an eta, a lag, an eel, a batik, a mug, amot, a nap, a maxim, a pat, a cud, a nu, a fan, a pal, a rum, a nod, an eta, a lag, an eel, a batik, a mug, amot, a nap, a maxim, a

mood, a leek, a grub, a gob, a gel, a drab, a citadel, a total, a cedar, a tap, a gag, a rat, a manor, a bar, a gal, mood, a leek, a grub, a gob, a gel, a drab, a citadel, a total, a cedar, a tap, a gag, a rat, a manor, a bar, a gal, a cola,a pap, a yaw, a tab, a raj, a gab, a nag, a pagan, a bag, a jar, a bat, a way, a papa, a local, a gar, a a cola,a pap, a yaw, a tab, a raj, a gab, a nag, a pagan, a bag, a jar, a bat, a way, a papa, a local, a gar, a

baron, a mat, a rag, a gap, a tar, a decal,a tot, a led, a tic, a bard, a leg, a bog, a burg, a keel, a doom, a mix, baron, a mat, a rag, a gap, a tar, a decal,a tot, a led, a tic, a bard, a leg, a bog, a burg, a keel, a doom, a mix, a map, an atom, a gum, a kit, a baleen, a gala, a ten, a don, a mural, apan, a faun, a ducat, a pagoda, a lob, a map, an atom, a gum, a kit, a baleen, a gala, a ten, a don, a mural, apan, a faun, a ducat, a pagoda, a lob, a rap, a keep, a nip, a gulp, a loop, a deer, a leer, a lever, a hair, a pad, a tapir, a door, a moor, an aid,a raid, a rap, a keep, a nip, a gulp, a loop, a deer, a leer, a lever, a hair, a pad, a tapir, a door, a moor, an aid,a raid,

a wad, an alias, an ox, an atlas, a bus, a madam, a jag, a saw, a mass, an anus, a gnat, a lab, a cadet, an a wad, an alias, an ox, an atlas, a bus, a madam, a jag, a saw, a mass, an anus, a gnat, a lab, a cadet, an em, a natural, a tip, acaress, a pass, a baronet, a minimax, a sari, a fall, a ballot, a knot, a pot, a rep, a carrot, em, a natural, a tip, acaress, a pass, a baronet, a minimax, a sari, a fall, a ballot, a knot, a pot, a rep, a carrot, a mart, a part, a tort, a gut, a poll, a gateway, alaw, a jay, a sap, a zag, a fat, a hall, a gamut, a dab, a can, a a mart, a part, a tort, a gut, a poll, a gateway, alaw, a jay, a sap, a zag, a fat, a hall, a gamut, a dab, a can, a tabu, a day, a batt, a waterfall, a patina, a nut, a flow, a lass, a van, a mow, anib, a draw, a regular, a call, a tabu, a day, a batt, a waterfall, a patina, a nut, a flow, a lass, a van, a mow, anib, a draw, a regular, a call, a

war, a stay, a gam, a yap, a cam, a ray, an ax, a tag, a wax, a paw, a cat, a valley, a drib, a lion, a saga, war, a stay, a gam, a yap, a cam, a ray, an ax, a tag, a wax, a paw, a cat, a valley, a drib, a lion, a saga, aplat, a catnip, a pooh, a rail, a calamus, a dairyman, a bater, a canal--Panama.aplat, a catnip, a pooh, a rail, a calamus, a dairyman, a bater, a canal--Panama.

The mother of all palindromesThe mother of all palindromes

palindromepalindrome

Disruption of a gene due to _______________ of a transposable element

Disruption of a gene due to _______________ of a transposable element

Mutation (cont.)Mutation (cont.)

Causes:Causes:SpontaneousSpontaneous -- due to ________________ -- due to ________________

mistakes or background effectsmistakes or background effects Frequency varies from 1 in ______ to 1 in _______ Frequency varies from 1 in ______ to 1 in _______

depending on organismdepending on organism Bacteria have such short generation times and grow Bacteria have such short generation times and grow

to such high populations that spontaneous mutants to such high populations that spontaneous mutants can be isolated quickly and easilycan be isolated quickly and easily

InducedInduced -- exposure to -- exposure to mutagensmutagens such as such as ______________ or _______________________________ or _________________

Spontaneous (antibiotic) mutantsSpontaneous (antibiotic) mutants

Mutagenesis by electromagnetic radiationMutagenesis by electromagnetic radiation

Chemical mutagenesisChemical mutagenesis

Horizontal gene transfer in bacteriaHorizontal gene transfer in bacteria

ConjugationConjugation -- direct (________________) -- direct (________________)

transfer between bacteriatransfer between bacteria

TransformationTransformation -- uptake of naked, -- uptake of naked,

__________________ DNA (often plasmids)__________________ DNA (often plasmids)

TransductionTransduction -- transfer of DNA from one cell -- transfer of DNA from one cell

to another by a _____________.to another by a _____________.

ConjugationConjugation

A A copycopy of the plasmid is made in of the plasmid is made in the recipient cell, resulting in a the recipient cell, resulting in a

plasmid in each cellplasmid in each cell

Text, Fig. 9.27Text, Fig. 9.27

________________________________________

Donor cell dies and Donor cell dies and lyses, releasing DNAlyses, releasing DNA

The free DNA is The free DNA is taken up by a taken up by a

recipient cell, and recipient cell, and incorporated into incorporated into

its genomeits genome

Griffith’s classic experiment in transformation Fig. 9.28Fig. 9.28

____________________________________

Text, Fig. 9.29Text, Fig. 9.29

How is the DNA incorporated?How is the DNA incorporated?

homologous recombinationhomologous recombination -- -- genetic exchange genetic exchange between (nearly) _________________ DNA sequences between (nearly) _________________ DNA sequences from 2 different sourcesfrom 2 different sources

________________ into chromosome________________ into chromosome

not incorporated into genome at all, but still not incorporated into genome at all, but still functional -- e.g. plasmidsfunctional -- e.g. plasmids