Question: A piranha plant with large spots is mated to a piranha plant with no spots. The F1 progeny all ha…

A piranha plant with large spots is mated to a piranha plant
with no spots. The F1 progeny all have medium sized spots. The F1
was self-crossed and the F2 showed a wide range of spot sizes. Out
of 1000 F2 piranha plants, only 4 individuals do not have spots.
How many genes are contributing to spot size?