A true-breeding plant with red fruit is crossed with a true-breeding plant with orange fruit. All of the F1 plants are red, but when these are crossed, the F2 plants consist of 135 red and 105 orange (this is NOT a 3:1 ratio).

This result suggests that:

Answer
a.
fruit color is determined by recessive epistasis.
b.
fruit color is determined by complementary gene action.
c.
red fruit is completely dominant to orange fruit.
d.
fruit color is determined by alleles of a single gene.

Question

A true-breeding plant with red fruit is crossed with a true-breeding plant with orange fruit. All of the F1 plants are red, but when these are crossed, the F2 plants consist of 135 red and 105 orange (this is NOT a 3:1 ratio).

This result suggests that:

Answer
	 a.	
fruit color is determined by recessive epistasis.
	 b.	
fruit color is determined by complementary gene action.
	 c.	
red fruit is completely dominant to orange fruit.
	 d.	
fruit color is determined by alleles of a single gene.

anonymous · Answer

@alphadxg It is B. In recessive epistasis you would expect a ratio with three "terms" while in B you expect a 9:7 ratio. It cannot be C because there would only be red fruit, and if was determined by alleles of a single gene it should either have 3:1 ratio. This is a nice pdf for more info: https://www.mcdb.ucla.edu/Research/Jacobsen/LabWebSite/LS4Class/Steve/13Fall/JacobsenLec5_13.pdf Oh, 135:105 is a 9:7 ratio.

alphadxg · Answer

:)

anonymous · Answer

@alphadxg I see my last bit was missed. If it was a single gene to get a ratio besides 3:1 I would expect something really odd, like a freak mutation happened.