The automated DNA sequencing machines utilize fluorescent dyes to detect the nascent DNA chains synthesized in the presence of the four dideoxy (ddX) chain terminators, each labeled with a different fluorescent dye. The dyes fluoresce at different wavelengths, which are recorded by a photocell as the products of the reactions are separated based on length by capillary gel electrophoresis (see Figure 14.17). In the standard sequencing reaction, the chains terminating with ddG fluoresce dark blue (peaks appear black in computer printout), those terminating with ddC fluoresce light blue, those terminating with ddA fluoresce green, and those terminating with ddT fluoresce red. The computer printout for the sequence of a short segment of DNA is shown as follows.

What is the nucleotide sequence of the nascent strand of DNA? What is the nucleotide sequence of the DNA template strand?

Transcribed Image Text:

First nucleotide Last nucleotide