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“I have set before you life and death, blessing and cursing; therefore choose life”

Deuteronomy 30:19

As the HELICASE proceeds to ‘unzip’ the DNA strands, there are at least two potential dangers

Direction of travel

HELICASE

The opened DNA strands are very fragile and they have a natural tendency to close up again. SINGLE-STRAND BINDING PROTEINS (SSBP) bind to the DNA strands exposed by the unwinding process. This strengthens the strands and prevents them from immediately reconnecting. It essential that the two backbone strands be kept apart to allow the PHOTOCOPIER to do its work. More about the ‘photocopier’ later.

HELICASE

Single Strand Binding Protein

DANGER AREA

HELICASE

The unwinding process causes torsional stress in the DNA downstream

This torsional stress can cause SUPERCOILING. Imagine you had an elastic band and you twisted it and kept on twisting it. Eventually it would become knotted and kinked. This is called supercoiling. Those of us who are old enough to remember the pre-cordless telephones, will recall that the cord linking the handset to the phone, would, after a good length of time, become twisted, gnarled and kinked. It was certainly a nuisance to use such a handset!

SSBP

Onto the DNA stage steps Miss Gillian Gyrase: the wizard with the scissors!

Silky smooth scissors!

CREATION

Part Two

Page 1

JUMPING

PAGES