The DNA to be sequenced is prepared as a single strand.
This template DNA is supplied with
• a mixture of all four normal (deoxy) nucleotides in ample quantities
o dATP
o dGTP
o dCTP
o dTTP
• a mixture of all four dideoxynucleotides, each present in limiting quantities and each labeled with a "tag" that fluoresces a different color:
o ddATP
o ddGTP
o ddCTP
o ddTTP
• DNA polymerase I
Because all four normal nucleotides are present, chain elongation proceeds normally until, by chance, DNA polymerase inserts a dideoxy nucleotide (shown as colored letters) instead of the normal deoxynucleotide (shown as vertical lines). If the ratio of normal nucleotide to the dideoxy versions is high enough, some DNA strands will succeed in adding several hundred nucleotides before insertion of the dideoxy version halts the process.
This template DNA is supplied with
o dATP
o dGTP
o dCTP
o dTTP
• a mixture of all four dideoxynucleotides, each present in limiting quantities and each labeled with a "tag" that fluoresces a different color:
o ddATP
o ddGTP
o ddCTP
o ddTTP
• DNA polymerase I
Because all four normal nucleotides are present, chain elongation proceeds normally until, by chance, DNA polymerase inserts a dideoxy nucleotide (shown as colored letters) instead of the normal deoxynucleotide (shown as vertical lines). If the ratio of normal nucleotide to the dideoxy versions is high enough, some DNA strands will succeed in adding several hundred nucleotides before insertion of the dideoxy version halts the process.