Question
Thu February 26, 2009 By:

PLS KINDLY EXPLAIN THE TOPIC OF DNA COPYING

Expert Reply
Thu February 26, 2009

DNA replication is the process of copying a double-stranded DNA molecule to form two double-stranded DNA molecules.

DNA replication is the basis for biological inheritance. It is a fundamental process occurring in all living organisms to copy their DNA. This process is semiconservative in that each strand of the original double-stranded DNA molecule serves as template for the reproduction of the complementary strand. Hence, following DNA replication, two identical DNA molecules are produced from a single double-stranded DNA molecule. Cellular proofreading and error-checking mechanisms ensure near perfect fidelity for DNA replication.

In a cell, DNA replication begins at specific locations in the genome, called origins. The length of the DNA double helix about to be copied is unwound at the origin. In addition, the two strands are separated, by breaking the weak hydrogen bonds that link the paired bases. Once the DNA strands have been unwound, they are held apart to expose the bases so that new nucleotide partners can hydrogen-bond to them. Unwinding of DNA at the origin, and synthesis of new strands, forms a replication fork.
 
The enzyme
DNA polymerase then moves along the exposed DNA strand, joining newly arrived nucleotides into a new DNA strand that is  complementary to the template. In addition to DNA polymerase, a number of other proteins are associated with the fork and assist in the initiation and continuation of DNA synthesis. Each cell contains a family of more than 30 enzymes to ensure the accurate replication of DNA.

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