Structure od DNA

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AS Biology. Gnetic control of protein structure and function

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AS Biology. Gnetic control of protein structure and function

Sugar phosphate bonds (backbone of DNA)

Nucleotides are connected to each other via the phosphate on one nucleotide and the sugar on the next nucleotide

A Polynucleotide

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AS Biology. Gnetic control of protein structure and function

James Watson (L) and Francis Crick (R), and the model they built of the structure of DNA

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AS Biology. Gnetic control of protein structure and function

X-ray diffraction photograph of the DNA double helix

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AS Biology. Gnetic control of protein structure and function

Base pairing

The Nitrogenous Bases pair up with other bases. For example the bases of one strand of DNA base pair with the bases on the opposite strand of the DNA.

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AS Biology. Gnetic control of protein structure and function

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AS Biology. Gnetic control of protein structure and function

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AS Biology. Gnetic control of protein structure and function

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AS Biology. Gnetic control of protein structure and function

The Rule:

Adenine always base pairs with Thymine (or Uracil if RNA)

Cytosine always base pairs with Guanine.

This is beacuse there is exactly enough room for one purine and one pyramide base between the two polynucleotide strands of DNA.

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AS Biology. Gnetic control of protein structure and function

Complementary base pairing

Purines Pyramidines

Adenine Thymine

Adenine Uracil

Guanine Cytosine

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AS Biology. Gnetic control of protein structure and function

Nature of the Genetic Material

Property 1 - it must contain, in a stable form, information encoding the organism’s structure, function, development and reproduction

Property 2 - it must replicate accurately so progeny cells have the same genetic makeup