standard recombination between an f’ and the chromosome
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Standard recombination between an F’ and the chromosome
Recombination between an F’ and a strain with a deletion (this doesn’t
give Lac+)
Recombination between an F’ and a strain with a deletion (this does give
Lac+)
Jeffery Miller made a series of ordered
deletions of the lacI gene
Ach!! about 1 amino acid apart!
He used these map mutations in lacI
An example from Miller’s workSchmeissner_JMB_1977
Horizontal red lines show where the mutations must lie—between the endpoints ofthe deletions to their immediate left and right
LacI monomer
LacI dimer bound to lacO
LacI dimer bound to DNA w/ HTH shown
Close up of LacI HTH bound to DNA
Binding of regulators to DNA is often at inverted repeats
Regulator proteins bind asback-to-back dimer. This puts each binding domainin the right orientation withrespect to the inverted repeat(protein toe binds 5’ end, heelbinds 3’ end of the repeat)
Binding siteshave invertedrepeats
Inverted repeats areon the same sideof the helix (spaced~10 bp apart)
LacI dimer forms back to back
Other Helix-Turn-Helix (HTH) DNA-binding proteins
TraR repressor Crp activator
Close up of Crp HTH bound to lac DNA
Mutations that give rise to stop codons
Frequencies of lacI mutations generated by different mutagens
Locations of nonsense mutations in LacI
Locations of nonsense mutations in LacI
Activity of suppressed nonsense mutations
Recombination frequencies between closely linked nonsense mutations
lacI(amber1)xF’
lacI(amber2)
How frequent are LacI+ relative to
distance separating the two mutations?
Would expect that mutations that are
close together would recombine
less that ones that are far apart
Location of mutations in lacI that give different lacI phenotypes
cAMP levels during growth of E. coli
Effect of cAMP on LacZ induction
Note that cAMP has less effect on induction on poor carbon sources than on glucose—Why is this?
cAMP alleviates
diauxic growth
Adenyl cyclase activities of various E. coli strains
Effect of cAMP on cya mutants
1100110053365336
Correlation of physical and genetic maps
Answers “where are mutations located in a particular piece of genetic material”
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