DNA &n Gene Expression

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DNA is a polymer of nucleotides & so is a polynucleotide.
Nucleotides are made up of:
a phosphate.
a sugar - deoxyribose.
a base - either adenine, guanine, thymine or cytosine
The nucleotides are arranged in two chains which are coiled
into a spiral shape called a double helix.
DNA has 3 parts. These are a pentose sugar called
deoxyribose, a phosphate group and a nitrogenous base.
The sugar and the phosphate are exactly the same in every
nucleotide, but the base varies. There are four bases in
DNA and each nucleotide contains one of them. The bases

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Adenine, Guanine, Thymine and Cytosine. (A,G,T
and C for short).
The nucleotides are joined in a specific order. The order of
the nucleotides means that the bases they contain are in a
certain order, it is this order which forms the genetic code.
sugar-phosphate-sugar bond is called a phosphodiester
DNA is the molecule which controls the synthesis of
proteins. Proteins are used for growth and repair and also
as enzymes.…read more

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Within any given cell, some
genes will be "on" or "off."
When a gene is "on," it is making proteins or RNA
products and affecting the functioning of the organism in
some way. If a gene is "on," scientists consider that it is
being expressed.…read more


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