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In a population of 34 S - AQA - A-Level Biology - Question 1 - 2021 - Paper 1
Question 1
In a population of 34 S. carolinensis, 2 had black fur. Use the Hardy-Weinberg equation to estimate how many squirrels in this population had brown-black fur. Show y... show full transcript
Worked Solution & Example Answer:In a population of 34 S - AQA - A-Level Biology - Question 1 - 2021 - Paper 1
Step 1
Use Hardy-Weinberg Equation
Answer
To estimate how many squirrels had brown-black fur, we start by applying the Hardy-Weinberg equation. Given:
Let p be the frequency of the Cg allele and q be the frequency of the Cb allele, we know that:
From the observed data, the number of individuals with black fur (Cc) is 2, hence:
The genotype frequency for black fur (Cc) can be represented as:
Next, solve for q:
Thus, the estimated frequency of the Cg allele (p) is: $$p = 1 - q = 1 - 0.242 = 0.758$$ Now we can find the expected number of individuals with brown-black fur (Cc), which can be calculated as p squared: $$2pq = 2(0.758)(0.242) \approx 0.3678 imes 34 \approx 12.5$$ Rounding gives approximately 13 squirrels.Step 2
Calculate Frequency of Cg Allele
Answer
Now, we need to find the actual frequency of the Cg allele in the population. From the total population of 34 squirrels, the count with brown-black fur is given as 16.
In the total population of 34:
We know that Cg alleles contribute to brown-black fur, therefore:
Counting alleles: Total alleles = 34 squirrels × 2 alleles = 68 alleles.
From the brown-black fur count (16), assuming their genotypes are CgCg or CgCc, we get:
Since brown-black fur incidence indicates presence of Cg, we can determine: Let x be the number of Cg alleles in brown-black squirrels. Thus:
Total number of Cg alleles can be estimated (from parents and offsprings), and calculating frequencies can be given by: Where n is Cg(Cg) counts, and m is for CgCc counts. Using the estimates:
From 34 squirrels, the frequency = 0.71.
Step 3
Step 4