how DNA duplicated?

Answer 1

a slightly longer answer...

DNA molecules are the shape of a double helix, like a twisted ladder.

Each rung of the ladder is made up of a pair of base nucleotides - Adenine, Guanine, Cytosine and Thymine.

A will always pair with T, G with C

When DNA wants to replicate (well when the cell instructs it to, DNA doesn't think or anything) an exnzyme comes along and starts to 'unzip' the DNA. this doesn't need to occur at one end, it can bulge in the middle and replicate in both ways.

It unzips the DNA to expose a single base on each rung of the ladder. With the assistance of many other cell parts and proteins, the cell bodies working on the DNA locate the required nucleotide (A, G, C,T) and essentially stick it onto its pair. So this way you end up with two new ladders. Then complex sugars form the sides of the ladder and the DNA retwists back into its chromosome formation.

Its a simple concept, but requires a lot of different cell organelles, and proteins to occur.

Answer 2

The short answer is: DNA polymerase duplicates DNA in the S phase of prophase.

Answer 3

After mitosis - in interphase. each and each chromatid is already created from 2 helices intertwined. They pull aside, the nucleus reforms and the cellular divides and the cellular is in interphase. The DNA makes it is supplement from that.