The DNA strand 3'0-GACTATTCCGACCC-5' is being sequenced using the dideoxy method.One reaction mixture contains all four deoxynucleoside triphosphates (dATP, dTTP, dCTP, dGTP)and a small amount (10%)of dideoxythymidine (ddTTP).After synthesis is completed, what sized bands will appear in the gel? (Assume that the primer is present but not counted in the size of any of the bands.)

Question

Quizplus · Accepted Answer

The dideoxy method terminates DNA synthesis at the nucleotide complementary to the dideoxynucleotide present in the reaction. Since ddTTP is used, synthesis will terminate at adenines (A) on the template strand. Reading the template strand from 3' to 5' to match the 5' to 3' synthesis direction, the adenines are at positions 2, 5, and 11, resulting in bands of 2-bp, 5-bp, and 11-bp.

The DNA Strand 3'0-GACTATTCCGACCC-5' Is Being Sequenced Using the Dideoxy