how is an in vitro dna replication system different from transcription and translation systems? what components would be needed to achieve replication in vitro

Answer 1

Great question! The goal of DNA replication is to copy the sequence of both strands of a DNA molecule and make two more molecules of DNA, while the goal of transcription is to simply copy the DNA sequence unto a single stranded mRNA message. Therefore the main difference relies on the enzymes that do these jobs. For DNA replication, two DNA polymerases are needed for each of the DNA strands. These DNA polymerases read the DNA sequence and add paired nucleotides. For transcription, an RNA Polymerase 2 is needed as it can read DNA but synthesize mRNA subunits. For translation, which occurs after transcription and it's goal is to synthesize peptides from mRNA, you would need the translational machinery consisting of ribosomal subunits, tRNAs, and translation factors. To expand on the other components needed for DNA replication, first you would need an enzyme that will loosen the DNA double helix structure. This enzyme is called a topoisomerase, it will unwind the DNA. Then, you will need an enzyme that will separate the two DNA strands, this enzyme is called a helicase. You also would need an RNA Primase that will synthesize a single RNA primer for the leading strand and multiple RNA primers for the lagging strand. Finally, you need a DNA ligase to ligate the Okazaki fragments on the lagging strand.