Dec 10

Here is a sequencing gel; each lane has products of a sequencing reaction (template DNA, short labeled primer, polymerase and nucleotides dATP, dCTP, dGTP, dTTP). Lane 1 also has a small amount of di-deoxyATP added (ddATP), lane 2 has a small amount of ddCTP, etc. The gel has single-stranded DNA, so only the newly synthesized (and labeled) DNA shows up. Remember that the smallest fragments migrate farthest down the gel. (Top of gel) A C G T _ _ _ _ (_) _ _ _ _ _ _ What is the sequence of this DNA? Label the 5’ and 3’ ends. What is at the 3’ end of the fragment in parentheses?

Sequence is 5’GTGGAATCATC3’ The fragment in parentheses will have a di-deoxy thymidine at the 3’ end. (It won’t have an OH at the 3’ end, so that terminates the DNA synthesis).