Question

Imagine a dihybrid cross. if there are 100 progeny (we are talking about flies here), approximately how many flies would you expect to be homozygous recessive for both traits?

Answer 1

In a dihybrid cross, the ratio of the offspring is 
9-homozygous dominant for both traits
3-dominant for one trait and recessive for the other) 
3 -dominant for one trait and recessive for the other
1 - homozygous recessive for both traits


Therefore there will be one-sixteenth of homozygous recessive for both traits( 9+3+3+1=16) of a 100 flies in the next generation, or more precisely 6,25.