Plant height is a polygenic trait in a particular species - VCE - SSCE Biology - Question 26 - 2013 - Paper 1
Question 26
Plant height is a polygenic trait in a particular species. There are three independently segregating genes, each with two alleles, which determine the height of a pa... show full transcript
Worked Solution & Example Answer:Plant height is a polygenic trait in a particular species - VCE - SSCE Biology - Question 26 - 2013 - Paper 1
Step 1
Calculate the height from MM RR SS
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Answer
The genotype MM RR SS contributes:
From locus 1: 5 cm (from MM)
From locus 2: 5 cm (from RR)
From locus 3: 5 cm (from SS)
Total height = 5 + 5 + 5 = 15 cm
Step 2
Calculate the height from M'M' R'R' S'S'
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Answer
The genotype M'M' R'R' S'S' contributes:
From locus 1: 2 cm (from M')
From locus 2: 2 cm (from R')
From locus 3: 2 cm (from S')
Total height = 2 + 2 + 2 = 6 cm
Step 3
Calculate the overall expected height
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Answer
To find the expected height of the offspring:
Using heights from both parents:
Height from MM RR SS = 15 cm
Height from M'M' R'R' S'S' = 6 cm
The possible combinations of the two parental heights can result in:
Maximum height = 15 + 6 = 21 cm (total contribution of dominant alleles)
Minimum height = 15 - 6 = 9 cm (if recessive traits were fully expressed)
Middle ground = more complex patterns through combinations yielding 21 cm as the most likely viable height seen in offspring.
