DNA - a double helix of based pairs

A DNA molecule has two strands coiled together in the shape of a double helix (two spirals).

The two strands are held together by chemicals called bases. There are four different bases - Adenine (A), Cytosine (C), Guanine (G), Thymine (T).

The bases are paired, and they always pair up in the same way, it's always A-T, and C-G. This is called base pairing.

The base pairs are joined together by weak hydrogen bonds.

A gene is a section of DNA, and the sequence of bases in a gene code for a specific protein.

Rosalind Franklin and Maurice Wilkins worked out that DNA had a helical structure by directing beams of x-rays onto crystallised DNA and looking at patterns the x-rays formed as they bounced off.

James Watson and Francis Crick used…


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