Figure 3.

Synthesis of photoreactive DNA probe. (A) A scheme illustrating in situ conversion of radiolabeled DNA₁ to the nicked DNA₂ containing FAB-dCMP and deoxyribose phosphate at 3′ and 5′ margins, respectively, of the nick. (B) Photograph of an autoradiogram of a DNA sequencing gel showing primer extension with FAB-dCMP and dCMP by the MEF extract. DNA₁ was incubated for 30 min at 25°C with MEF extract and products were analyzed as described in the Materials and Methods. Lane 1, DNA₁ was incubated with MEF extract without FAB-dCTP; lane 2, DNA₁ was incubated with MEF extract and FAB-dCTP; lane 3, DNA₁ was incubated with MEF extract, FAB-dCTP and Pyr-dUTP; lane 4, DNA₁ was incubated with MEF extract and dCTP (10 µM). The positions of the primer and the products are indicated.