In a hypothetical plant species, flower color is determined by the following bio
ID: 204126 • Letter: I
Question
In a hypothetical plant species, flower color is determined by the following biochemical pathway:
I
A B C D
Colorless -------> Yellow --------> Orange --------> Red ----------> Purple
Genes A, B, C, D and I are independently assorting. The dominant alleles, A, B, C, and D, encode active enzymes that catalyze the corresponding reactions, and the recessive alleles, a, b, c, and d are nonfunctional. The dominant I allele totally inhibits the action of gene C, while i has no effect.
a. A cross is made between AAbbCCDDII and AABBCCDDii plants. What is the genotype and phenotype of the F1 plants?
b. These F1 plants are self-crossed. What is the phenotypic ratio of the resultant F2 generation?
c. What proportion of the offspring of an AaBBCCDdIi x AaBBCcDdIi cross is expected to have colored flowers?
Explanation / Answer
Answer:
A).
AAbbCCDDII (yellow) x AABBCCDDii (purple)
AbCDI ABCDi ------Gametes
AABbCCDDIi (Orange)-------F1
b).
AABbCCDDIi x AABbCCDDIi -----Selfcross
ABCDI
ABCDi
AbCDI
AbCDi
ABCDI
AABBCCDDII (orange)
AABBCCDDIi (orange)
AABbCCDDII (orange)
AABbCCDDIi (orange)
ABCDi
AABBCCDDIi (orange)
AABBCCDDii (purple)
AABbCCDDIi (orange)
AABbCCDDii (purple)
AbCDI
AABbCCDDII (orange)
AABbCCDDIi (orange)
AAbbCCDDII (yellow)
AAbbCCDDIi (yellow)
AbCDi
AABbCCDDIi (orange)
AABbCCDDii (purple)
AAbbCCDDIi (yellow)
AAbbCCDDii (yellow)
Orange = 9/16
Purple = 3/16
Yellow = 4/16
c).
AaBBCCDdIi x AaBBCcDdIi
Aa x Aa = A_ (3/4) & aa (1/4)
If both the “A” alleles are not available, all phenotypes are colorless.
So the probability of colorless = 1/4
ABCDI
ABCDi
AbCDI
AbCDi
ABCDI
AABBCCDDII (orange)
AABBCCDDIi (orange)
AABbCCDDII (orange)
AABbCCDDIi (orange)
ABCDi
AABBCCDDIi (orange)
AABBCCDDii (purple)
AABbCCDDIi (orange)
AABbCCDDii (purple)
AbCDI
AABbCCDDII (orange)
AABbCCDDIi (orange)
AAbbCCDDII (yellow)
AAbbCCDDIi (yellow)
AbCDi
AABbCCDDIi (orange)
AABbCCDDii (purple)
AAbbCCDDIi (yellow)
AAbbCCDDii (yellow)
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