With fully automated Sanger sequencing, all four chain-terminating ddNTPs can be added into a single reaction. This is different from the traditional slab gel Sanger sequencing, where a different reaction had to be carried out for each ddNTP

Question

The mixing of all four ddNTPs can be carried out because ______________.
(a) the fully automated Sanger sequencing reactions are loaded onto a capillary gel.
(b) the fully automated Sanger sequencing reactions utilize ddNTPs each labeled with a different fluorescent tag, which allows all four ddNTPs to be incorporated into a single molecule of DNA.
(c) the fully automated Sanger sequencing reactions generate a set of products, each of which carries a single fluorescent tag whose color reveals the identity of the base that is at the end of the product.
(d) the fully automated Sanger sequencing reactions do not require DNA polymerase because the bases are read as the DNA is pulled through a tiny pore at the end of the capillary gel.

Answer 1

Choice (c) is correct. Although it is true that fully automated Sanger sequencing requires a capillary gel, this is not why all four ddNTPs can be mixed in a single reaction [choice (a)]. Ideally, a single ddNTP is incorporated into each product; all four ddNTPs should not be incorporated into a single product [choice (b)]. Fully automated Sanger sequencing still requires DNA polymerase, and reads the fluorescent ddNTP at the end of each product [choice (d)].