KEGS Biology Blog

Monday 5th November Section 1
November 5, 2012, 1:30 pm
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DNA – (Semi-Conservative) Replication:
In order for semi-conservative replication to occur the DNA first needs to unwind and is done so by the enzyme, DNA Helicase, which separates the chain and exposes the nitrogenous bases. Then each chain acts as a template so new chains can be built. DNA Polymerase (another enzyme) proof reads the nucleotides, ensuring they join up in the right order (correct pairing i.e. adenine and thymine) and the hydrogen bonds then form between the bases and the DNA zips back up. Therefore, there are two new strands and each strand consists of one conserved strand and one new strand.

There are two hydrogen bonds between the bases adenine and thymine whereas there are three hydrogen bonds between the bases cytosine and guanine.
Adenine and guanine are purines but thymine and guanine are pyrimidines.

Four key structural points on DNA:
– The DNA molecule is long to allow a large amount of information to be stored
– The base pairing rule means that the complimentary strands can be replicated
– The double helix gives the molecule stability
– Hydrogen bonds allow easy unzipping for copying and reading information

Comment by danielwatt

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