Question

What are the major essential components of the bacterial replisome and what are their functions? What is the direction of chain-growth in DNA synthesis? RNA synthesis? Polypeptide synthesis?

Answer 1

Components	Function
Helicase	Uncoils 2 DNA strand
DNA polymerase	Polymerizes the polynucleotide chain and helps in synthesis of DNA.
Primase	Synthesizes RNA primer required for initiating the process of replication
Single strand binding protein	Prevents reannealing of the separated ssDNA.
Beta clamp	Prevents the DNA polymerase to fall off, it increases the processivity of the polymerase
Topoisomerase	Prevents supercoiling of the DNA by introducing DNA strand breaks

The components of bacterial replisome and their functions are given in the table above.

The direction of the processes are given below.

Process	Direction
Replication (DNA synthesis)	Leading strand in 5’ to 3’ direction. The lagging strand synthesis also occurs in 5’to 3’ direction with the assistance of okazaki fragments.
Transcription (RNA synthesis)	RNA polymerases synthesizes RNA in 5’ to 3’ direction
Translation (protein synthesis)	Synthesis occurs in 5' -> 3' direcion. Upstream of the start codon AUG the mRNA contains 5’ UTR which is a regulatory, untranslated region.