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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 parental genotypes for violet eggplants can be defined as follows:

Dark purple: PP (homozygous dominant)
White: WW (homozygous recessive)
Violet: PW (heterozygous)

Since two violet offspring are being crossed, their genotypes will both be PW.

Step 2

Set up the Punnett square

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Answer

To find the phenotypic ratio, we can set up a Punnett square for the cross of the two violet eggplants (PW x PW):

      P   W
    ---------
  P |  PP | PW |
    ---------
  W |  PW | WW |
    ---------

From this Punnett square, we can see the possible genotypes for the offspring:

Step 3

Determine the phenotypic ratio

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Answer

The resulting genotypes from the cross are:

PP (dark purple)
PW (violet)
WW (white)

Now, counting the phenotypes:

Dark purple: 1
Violet: 2
White: 1

Thus, the phenotypic ratio is:

Dark purple : Violet : White = 1 : 2 : 1

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