Two points separated by 80 bp in the free double helix may actually be one on another on nucleosome surface.

 

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#Id: 3221

#Unit 4. Cell Communication and Cell Signaling

Direct-carcinogens includes:

Ethylmethane sulfonate (EMS)
Dimethyl sulfate (DMS)
Nitrogen mustards

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#Id: 3223

#Unit 4. Cell Communication and Cell Signaling

Indirect-acting carcinogens

Relatively unreactive compounds that become modified to more reactive forms by cellular cytochrome P-450 enzymes

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#Id: 3225

#Unit 4. Cell Communication and Cell Signaling

Benzo(a)pyrene, found in cigarette smoke as well as in coal tar, undergoes metabolic activation by cytochrome P-450 in the lungs to form a potent mutagen.

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#Id: 3227

#Unit 4. Cell Communication and Cell Signaling

P-450 enzymes, modify benzo(a)pyrene in a series of reactions, producing 7,8-diol-9,10-epoxide, a highly potent mutagenic species.

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#Id: 3229

#Unit 4. Cell Communication and Cell Signaling

7,8-diol-9,10-epoxide is responsible for cancer development forms an adduct with guanine:

(+)-trans-anti-B-(a)-P-N superscript 2-d G adduct

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#Id: 3231

#Unit 4. Cell Communication and Cell Signaling

(+)-trans-anti-B-(a)-P-N superscript 2-d G adduct causes polymerase to insert an A rather than a C opposite the modified G base (Transversion mutation)