Two pigs, one with a 6 cm tail and one with a 30 cm tail were crossed. Their F1 offspring had tails of 18 cm. The F2 piglets had tails ranging in 4 cm intervals from 6 cm to 30 cm. Most had 18 cm tails. 1/64 had 6 cm tails and 1/64 had 30 cm tails.
Explain how tail length is inherited. Indicate how many gene pairs are at work and designate the genotypes of the two parents and lf the F1 offspring.