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Microbial Genetics. I. Structure and function of genes II. Gene expression in bacteria III. Mutation and variation IV. Horizontal gene transfer in bacteria. Levels at which enzymes can be regulated. In prokaryotes, expression is generally regulated at the level of _____________.
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Microbial Genetics I. Structure and function of genes II. Gene expression in bacteria III. Mutation and variation IV. Horizontal gene transfer in bacteria
Levels at which enzymes can be regulated In prokaryotes, expression is generally regulated at the level of _____________
In bacteria, genes are organized into operons • Operon -- a cluster of genes whose expression is controlled by a single operator. • Operator -- a specific region of the DNA at the initial end of a gene or operon, where a repressor protein binds and _______________ mRNA synthesis. • Repressor protein -- a regulatory protein that binds to specific sites on DNA and blocks ______________________ .
The lac Operon: an example of enzyme _____________ Repressor -galactosidase http://esg-www.mit.edu:8001/bio/pge/lac.html
When lactose is unavailable, the repressor is _____________. It binds to the operator region, blocking the binding of the ___________ ______________________. No mRNA and no protein Repressor http://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 __________________________ Blocked lactose http://esg-www.mit.edu:8001/bio/pge/lac.html
Review: lac operon without inducer (________________) http://www.biology.arizona.edu/molecular_bio/problem_sets/mol_genetics_of_prokaryotes/02t.html?
Review: lac operon with inducer (lactose) http://www.biology.arizona.edu/molecular_bio/problem_sets/mol_genetics_of_prokaryotes/02t.html?
An example of enzyme repression: the ________________ operon
Mutation • Any permanent, _______________ change in the genetic information of a cell. • Types: • Point mutations -- substitution, insertion, or deletion of _______________ or a few bases • Large insertions or ________________
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) Gene A
palindrome Palindromes: Go hang a salami, I'm a lasagna hog The mother of all palindromes 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, 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 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 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 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 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 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 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 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, aplat, a catnip, a pooh, a rail, a calamus, a dairyman, a bater, a canal--Panama. Transposable element G A C G T 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 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 G A C G T C T G C A G C T G C A
Disruption of a gene due to _______________ of a transposable element
Mutation (cont.) • Causes: • Spontaneous -- due to ________________ mistakes or background effects • Frequency varies from 1 in ______ to 1 in _______ depending on organism • Bacteria have such short generation times and grow to such high populations that spontaneous mutants can be isolated quickly and easily • Induced -- exposure to mutagens such as ______________ or _________________
Horizontal gene transfer in bacteria • Conjugation -- direct (________________) transfer between bacteria • Transformation -- uptake of naked, __________________ DNA (often plasmids) • Transduction -- transfer of DNA from one cell to another by a _____________.
Conjugation A copy of the plasmid is made in the recipient cell, resulting in a plasmid in each cell
____________________ Donor cell dies and lyses, releasing DNA The free DNA is taken up by a recipient cell, and incorporated into its genome
How is the DNA incorporated? • homologous recombination-- genetic exchange between (nearly) _________________ DNA sequences from 2 different sources • ________________ into chromosome • not incorporated into genome at all, but still functional -- e.g. plasmids
