How are additive alleles determined when examining polygenic inheritance?

Two pure-breeding lines of orange trees differ in the number of fruit segments they contain: One line produces fruit with 6 segments, and the other produces fruit with 10 segments. When these lines are crossed, the F1 produces fruit with 8 segments. When the F1 trees are crossed, the resulting F2 has nine phenotypic classes of trees, producing fruit with as few as 4 segments and as many as 12.

Assume that fruit segment number in orange trees is determined entirely by multiple unlinked, additive alleles.

1. The number of additive alleles in each F2 individual ranges from zero to _______.
2. The number of classes in the F2 indicates that this trait is controlled by _______ loci that differ in their alleles in the two pure lines.
3. The number of additive alleles in Line 1 is ________ the number of additive alleles in Line 2.


Choices for numbers 1 and 2:
Two, three, four, five, eight, nine, ten

Choices for number 3:
Less than, greater than, equal to