dideoxy DNA sequencing
Replication
of the DNA
strand in a sequencing reaction begins with (A)
a set of primed template ssDNA molecules, and
all four dNTPs plus one (B) ddNTP, in the example
ddATP. The -H
on the 3'-C prevents further extension. (C)
The region to be sequenced includes three T
positions. The ddATP is
randomly incoporated during strand synthesis, such
that chain growth terminates at each T
where
a complementary ddA
has been incorporated.
Four
separate
reactions with each of the four ddNTPs produces
a complete set
of
fragments that differ by plus or minus one nucleotide
over the entire length of the template DNA..
Figure © 2012 TA Brown, Introduction to Genetics (1st ed.); additional text © 2012 by Steven M. Carr