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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 talln... 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 and the ratio of phenotypes expected in the offspring of this cross.
Answer
Phenotypes of parents: Dwarf, pink-flowered × Tall, white-flowered
Genotypes of parents: ttCRcw × TTCRcw
Genotypes of offspring: 50% TtCRcw (tall, pink-flowered), 50% ttCRcw (dwarf, pink-flowered)
Phenotypes of offspring: 50% tall, pink-flowered; 50% dwarf, pink-flowered
Ratio of phenotypes: 1:1.
Step 4
Use the Hardy-Weinberg equation to calculate the percentage of pink-flowered plants in this population.
Answer
Let p = frequency of pink-flowered plants and q = frequency of red-flowered plants.
Given q^2 = 0.09 (9)% Thus, q = sqrt(0.09) = 0.3.
Using Hardy-Weinberg equation: p + q = 1, we find p = 1 - 0.3 = 0.7.
The percentage of pink-flowered plants = p^2 = (0.7)^2 = 0.49 or 49%.