Test Cross

[sylviej]

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I came across a question like this in Kaplan,
Red is dominant over white in a certain flower. To test whether a red offspring is homozyguous or heterozygous in this flower, one would
A)Cross it with a red plant that had a white parent
B)cross it with a red plant that had two red parents
C) Cross it with a white plant
D) B and C
E) None of them work

I think the answer should be C but the Kaplan answer is D. I went through Cliffs AP Biology, the example given in the book indicates crossing with recessive trait. I wonder which answer should I go with if a test cross problem comes up in real DAT?

 

[mvam]

typically cross tests are done with the homozygous recessive plant. i wouldn't be too tripped up on this specific question being asked on you're actual dat.

 

[BrazilianRider]

(B) makes absolutely no sense to me either... I mean I guess the red plant with red parents can be heterozygous and then if the tested plant is heterozygous you could get a white plant? But what happens if the red plant with red parents is homozygous? Then even if the plant you're testing is heterozygous, you won't be able to tell...

I'd stick with (C), until someone comes on here and proves us wrong.

 

[sylviej]

Thanks guys! Really appreciate it.