A true-breeding red snapdragon was crossed to a true-breeding white snapdragon.

Question

A true-breeding red snapdragon was crossed to a true-breeding white snapdragon. The F1 progeny were red. When the F1 were selfed, the following F2 progeny were
observed:

1850 red
670 pink
831 white
Total: 3351

(a) Using your own clearly defined genetic symbols, give the appropriate parental, F1,
and F2 genotypes in order to explain the above results.

(b) What phenotypic ratio would be expected from a testcross of an F1 snapdragon?

(c) Suppose the white phenotype is now lethal. What phenotypic ratio would be expected
from a cross between F1 individuals?


A
B
C
D
E
Mutation
1
-
-
-
-
+

2
-
+
+
+
+

3
-
-
+
+
+

4
-
-
+
-
+

Using the data above, construct a biochemical pathway indicating the order of the compounds. Explain how you arrived at the map.

Explanation / Answer

A true-breeding red snapdragon was crossed to a true-breeding white snapdragon. The F1 progeny were red. When the F1 were selfed, the following F2 progeny were observed: 1850 red 670 pink 831 white Total: 3351 (a) Using your own clearly defined genetic symbols, give the appropriate parental, F1, and F2 genotypes in order to explain the above results. (b) What phenotypic ratio would be expected from a testcross of an F1 snapdragon? incomplete dominance AA-------RED ,aa-white Aa-pink true-breeding red snapdragon was crossed to a true-breeding white snapdragon. AA-------RED x aa-white Aa-pink -----------------------F1 GENERATION Aa-pink X Aa-pink SELFING OF F1 GENERATION AA Aa Aa aa 1850 pink-------1/2 670 red---------1/4 831 white------1/4 Total: 3351

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