Final answer:
DNA ligase does not function at the origin of replication in E. coli; it works later by joining the Okazaki fragments. Other proteins like helicase, SSBs, DnaA, dnaB, and dnaC are involved in the replication initiation at the origin. The correct option is a. DNA ligase
Step-by-step explanation:
The protein that does not function at the origin of replication in E. coli is DNA ligase. DNA ligase has a function later in the replication process; it joins the Okazaki fragments on the lagging strand. Proteins such as helicase, SSBs (single-strand binding proteins), and DnaA, dnaB, and dnaC proteins are indeed involved at the origin of replication. Helicase unwinds the DNA strands, SSBs stabilize the unwound DNA, and the DnaA, dnaB, and dnaC proteins assist in the initiation of replication.
During Sanger sequencing, the addition of dideoxynucleotides prevents the further development of a DNA strand by terminating the elongation process. DNA replication proceeds in the 5' to 3' direction, as DNA polymerase can only add nucleotides to the 3' end of a growing DNA strand.
The correct option is a. DNA ligase