Eye colour is controlled by genes - Edexcel - GCSE Biology - Question 1 - 2016 - Paper 1
Question 1
Eye colour is controlled by genes.
The allele for brown eyes, B, is dominant to the allele for blue eyes, b.
(a) A female with blue eyes and a male with brown eyes ... show full transcript
Worked Solution & Example Answer:Eye colour is controlled by genes - Edexcel - GCSE Biology - Question 1 - 2016 - Paper 1
Step 1
Complete the Punnett square to determine the phenotype of the child.
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Answer
To complete the Punnett square, we must indicate the alleles from each parent:
B B
____________________
b Bb Bb
b Bb Bb
The possible offspring genotypes are Bb. Since brown (B) is dominant, all offspring will have brown eyes. Therefore, the phenotype of the child is brown eyes.
Step 2
Complete the tally chart, in Figure 2, for this data.
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Answer
Eye Colour
Tally
Total
Blue
Brown
Green
Hazel
Total
Step 3
Give another appropriate method of displaying this information.
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Answer
This data could be displayed as a bar chart or a pie chart, both of which effectively visualize the distribution of eye colours in the sample.
Step 4
Which sequence is the complementary DNA strand?
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Answer
The complementary DNA strand for the given sequence (ATGGCLTAAGTA) involves pairing each base with its complementary base:
A pairs with T
T pairs with A
G pairs with C
C pairs with G
Hence, the correct complementary strand is (D) GCATAGCAGC.
Step 5
Give a reason for filtering the mixture.
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Answer
Filtering the mixture is necessary to remove solid debris from the crushed fruit and to isolate the liquid containing the DNA from other cellular material.
Step 6
What is the role of the ethanol?
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Answer
The role of ethanol in the DNA extraction process is to precipitate the DNA. By adding ethanol, the DNA becomes visible as it aggregates and separates from the solution.
