The recombination counter

You will write three small functions for the results of a test cross with two linked genes.

The idea. The recombinants are the offspring that do not have a parental combination. The recombination frequency is their share of all the offspring, in per cent, and it is the distance in map units.

Your tasks.

1. Finish recombination_frequency. It takes a dictionary of counts and the list of the two parental kinds, and gives the frequency in per cent.
2. Finish middle_gene. It takes the three distances and gives the letter of the gene that lies in the middle.
3. Finish expected_recombinants. It gives the number of recombinant offspring expected from a number of offspring and a distance in map units.