explain briefly

Asked by adityasri | 6th Nov, 2008, 10:30: PM

Expert Answer:

DNA copying takes place through the process of DNA replication.

Since DNA is double stranded i.e. there are two sides to the double helix, each side can be used to make the other side due to complementary base pairing.



Steps in DNA Replication:

1) To unwind the DNA molecule by breaking the weak hydrogen bonds holding the two strands together. This is accomplished by the "unwinding" enzyme helicase.


2)  After the helicase has unwound the DNA molecule, DNA polymerase base pairs each exposed nucleotide with a new complementary nucleotide which occurs as nucleotide triphosphates in the nucleotide pool.

Important howeverthe replication can only proceed from a 31 to th e 51 direction of the original molecule

or in the 5' to 3' direction of the new molecule, therefore on the continuous (leading) strand, nucleotides are inserted in a smooth continuos manner (5' ----> 3'). But since the other strand is running in the wrong direction therefore the new nucleotides are linked into small segments called "Okazaki' fragments and inserted in the correct direction and joined by an enzyme called ligase.

The replication fork then can begin at several locations on the DNA molecule and proceed in both directions until the entire molecule is replicated.

This type of DNA replication then results in two identical copies of DNA. Each copy is made of one old strand from the original DNA molecule and one new strand from the nucleotide pool.



Answered by  | 7th Nov, 2008, 08:37: AM

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