JUST like twins recognising and approaching each other through a crowd at a party, identical stretches of double-stranded DNA will seek each other out.
Although we know that single complementary strands of DNA attract each other, such attraction was unheard of in zipped-up, double-stranded DNA, which must 鈥渦nzip鈥� itself before it can be copied or repaired. The finding could suggest a preparatory stage in the mechanism by which DNA repairs itself.
Alexei Kornyshev of Imperial College London and his team mixed together two distinct variants of double-stranded DNA in water. One was labelled with a fluorescent green marker and the other red. The team found that over time the reds and greens congregated with their own kind (The Journal of Physical Chemistry B, ).
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The researchers think the recognition results from complementary electrostatic attractions between identical regions of the double helix. The pairing balances negative charges in the sugar 鈥渂ackbone鈥� of one helix exactly with positive charges within the central 鈥済roove鈥� of the other helix. 鈥淭herefore, you鈥檇 get a symmetry,鈥� says Kornyshev. And the longer the strand, the stronger the attraction.
Kornyshev says the phenomenon might explain how identical DNA strands line themselves up ready for repairs, and for the shuffling that takes place when genes from each parent are mixed up during the formation of eggs and sperm.
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