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Mutation is one cause of genetic variation in organisms - AQA - A-Level Biology - Question 6 - 2020 - Paper 1
Question 6
Mutation is one cause of genetic variation in organisms. Give two other causes of genetic variation. 1 2 In a species of flowering plant, the T allele for tallnes... show full transcript
Worked Solution & Example Answer:Mutation is one cause of genetic variation in organisms - AQA - A-Level Biology - Question 6 - 2020 - Paper 1
Step 1
Step 2
Step 3
Complete the genetic diagram to show all the possible genotypes.
Answer
Phenotypes of parents: Dwarf, pink-flowered × Tall, white-flowered.
Genotypes of parents: Dwarf, pink-flowered: ttR<sup>Cr</sup> Tall, white-flowered: TtC<sup>W</sup>.
Genotypes of offspring: 1/2 TtR<sup>Cr</sup> (Tall, pink-flowered) and 1/2 ttC<sup>W</sup> (Dwarf, white-flowered).
Phenotypes of offspring: 1:1 ratio of Tall, pink-flowered to Dwarf, white-flowered.
Ratio of phenotypes: 1 Tall, pink-flowered: 1 Dwarf, white-flowered.
Step 4
Use the Hardy-Weinberg equation to calculate the percentage of pink-flowered plants in this population.
Answer
Given that 9% of the population contains red-flowered plants (q<sup>2</sup> = 0.09), we calculate q:
q = √0.09 = 0.3 for red flowers.
Since p + q = 1, p = 1 - q = 1 - 0.3 = 0.7.
Now we can find the percentage of pink-flowered plants using the Hardy-Weinberg formula: 2pq:
2pq = 2 * 0.7 * 0.3 = 0.42, which is 42%.