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Helix geometry

Once you have cross-linked seven or eight blue rods, pick a sugar ring (green connector) and follow its strand around the helix until you reach another sugar ring in the same orientation. This is one   helical turn and it occurs after reaching the sixth green connector (start counting with the first connector after the one you picked). The model has six base pairs (blue connectors) per helical turn. In the normal form of DNA, there are ten base pairs in one helical turn. Hold your model vertically. Notice that the base pairs are inclined. The angle they make with horizontal is close to 20 degrees. In normal DNA, the base pairs are nearly horizontal (the incline is -6 degrees).