Eggplant fruit comes in three colours: dark purple, white and violet - HSC - SSCE Biology - Question 22 - 2022 - Paper 1
Question 22
Eggplant fruit comes in three colours: dark purple, white and violet. A genetic cross between the dark purple and white eggplants will always result in the violet ph... show full transcript
Worked Solution & Example Answer:Eggplant fruit comes in three colours: dark purple, white and violet - HSC - SSCE Biology - Question 22 - 2022 - Paper 1
Step 1
Identify the parental genotypes
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Answer
The alleles for the colors of the eggplant are represented as follows:
Dark purple = PP
White = WW
Violet = PW
Since both dark purple and white are determined to be dominant and the violet color arises from mixing these two, the genotype for violet offspring is PW.
Step 2
Perform the cross between two violet offspring
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Answer
When two violet eggplants (PW) are crossed, the Punnett square would be:
P W
---------
P | PP | PW |
---------
W | PW | WW |
---------
This results in the following genotypes:
PP: 1 (Dark Purple)
PW: 2 (Violet)
WW: 1 (White)
Step 3
Determine the phenotypic ratio
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Answer
From the above genotypic ratio, the phenotypic ratio can be summarized as:
Dark Purple : Violet : White = 1 : 2 : 1
Thus, crossing two violet offspring results in a phenotypic ratio of 1:2:1.
