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adrii01 adrii01
wrote...
Posts: 55
9 years ago
A dark-red strain and a white strain of wheat are crossed and produce an intermediate, medium-red F1.
When the F1 plants are interbred, an F2 generation is produced in this ratio:
1 dark-red: 4 medium-dark-red: 6 medium-red: 4 light-red: 1 white

Further crosses reveal that the dark-red and white F2 plants are true breeding.

How many additive alleles are needed to produce each possible phenotype?
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wrote...
9 years ago
6
wrote...
Valued Member
On Hiatus
9 years ago
It is obvious that we are talking about 2 pair of alleles (4 alleles total), both responsible for the plant color. When all four alleles are "red" color, the plant is dark red. One, two, three or four of the "white" allele makes the plant from medium-dark red to completely white:
4 "red"= dark red color
3 "red" 1 "white"= medium- dark red color
2"red" 2 "white"= medium red colur
1 "red" 3 "white"= light- red color
4 "white" = white color

This is also confirmed if you make the crossings.

However, I can't quite understand the question "How many additive alleles are needed to produce each possible phenotype?" Of course, I know that the "red" and "white" alleles are additive. But I can't understand what it asks.
adrii01 Author
wrote...
9 years ago
All of them were right except for white. The correct answer was 0 white.
wrote...
Valued Member
On Hiatus
9 years ago
yes, that's why you need to read the reply carefully instead of just copying the answer. The white wheat didn't have any red alleles, and that's why I skipped them instead of writing 0 "red".

Anyways, I guess the exercise was asking for the number of red alleles. In my opinion, the question wasn't very accurate.
wrote...
3 years ago
Thank you, nice explanation
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