(c)+DNA+Replication+(Q+10-13)



DNA replication is the copy of the coded instructions within a section of DNA in order for one organism to pass down genetic characteristics onto its offspring or for synthesis of new cells which is required for growth. The replication of DNA must be carried out with great accuracy, since a change in characteristics might be harmful to the organism. In an organism, the replication of DNA is a vital part of cell division, which is done through a process called mitosis – where the mother cell divides and produces two daughter cells (Steane). Cell division is essential for growth and development of organisms.



The DNA molecule is made up of nucleotides. Each nucleotide contains a base and a sugar-phosphate backbone.

The base pairing rule means that the coded sequence on one chain of the double helix automatically determines the coded sequence on the other chain, ensuring accurate replication. The four bases found in DNA are adenine (A), cytosine (C), guanine (G) and thymine (T). The base pairing rules for DNA are:
 * A pairs with T
 * G pairs with C
 * C pairs with G
 * T pairs with A



During DNA replication, the two strands (sides) of the DNA are unwinded (unzipped) into individual strands. An enzyme called the Helicase is responsible for this job. Each strand acts as a template for making another strand using a supply of nucleotides that float within the nucleus. Based on the base pairing rule above, the order of bases on each new strand is determined by the order of bases on the template.

DNA consists of polymers called nucleotides (see above). The separated strand of DNA each form a new DNA as the each nucleotide is matched against each respective pair (see base pairing rules) by an enzyme called DNA polymerase III helps finding the repective match. The enzyme DNA ligase helps attach the DNA nucleotides together.

Now two identical strands of DNA are formed, each containing one old strand and one new one. Each DNA strand is identical to each other and to the original one.



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