DNA REPLICATION PROCESS

1.)

The DNA helices begin unwinding from the nucleosomes.

2.)

A helicase enzyme untwists the double helix and gradually separates the DNA molecule into two complementary nucleotide chains, exposing the nitrogenous bases.

3.)

Each nucleotide strand then serves as a template, or set of instructions,for building a new complementary nucleotide strand from free DNA precursors dissolved in the nucleoplasm.

4.)

At sites where DNA synthesis is to occur, the needed "machinery" gradually accumulates until several different proteins a represent in a large complex called a replisome.the actual initiation of DNA synthesis requires formation of short RNA primers. They are eventually replaced by DNA nucleotides.

5.)

Once the primer is in place, DNA polymerase III, comes into place. Continuing from the primer, it positions complementary nucleotides along the template strand and then covalent lay links them together. One strand then, the leading strand, is synthesized continuously following the movement of the replication fork. The other strand, called the lagging strand, is constructed in segments in the opposite direction and it requires that a primer initiate replication of each segment.

6.)

The short segments of DNA are then spliced together by DNA ligase. The end result is that two DNA molecules are formed from the original DNA helix and are identical to it.

7.)

As soon as replication ends, histones associate with the DNA, completing the formation of two new chromatin strands. The chromatin strands, united by a button like centromere, condense to form chromatids. The chromatids remain attached, held together by the centromere and a protein complex called cohesion, until the cell has entered the anaphase stage of milo tic cell division. They are then distributed to the daughter cells ensuring that each has identical genetic information.