The strand reader

A piece of DNA is written as a string of letters from the 5′ end to the 3′ end. You will make its partner strand, find its G-C content and count its hydrogen bonds.

The idea. Each base pairs with one other base. The partner strand runs the other way, so it must be turned round to be read from its 5′ end.

Your tasks.

1. Finish partner. It gives the partner strand, read from its 5′ end to its 3′ end.
2. Finish gc_percent. It gives the per cent of G and C in the strand.
3. Finish bonds. It gives the number of hydrogen bonds in the double helix: 2 for each A-T pair and 3 for each G-C pair.