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Eye colour is controlled by genes - Edexcel - GCSE Biology Combined Science - 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 a... show full transcript
Worked Solution & Example Answer:Eye colour is controlled by genes - Edexcel - GCSE Biology Combined Science - Question 1 - 2016 - Paper 1
Step 1
Complete the Punnett square to determine the phenotype of the child.
Answer
To complete the Punnett square, we start with the alleles:
- The woman has blue eyes, represented by the genotype 'bb'.
- The man has brown eyes, but since brown is dominant, he must have the genotype 'Bb'.
The completed Punnett square is as follows:
B b
------------
b | Bb | bb |
------------
b | Bb | bb |
------------
From the Punnett square, we can see that the offspring genotype ratios are 50% Bb (brown eyes) and 50% bb (blue eyes). Therefore, the phenotype of the child will be brown eyes.
Step 2
Complete the tally chart, in Figure 2, for this data.
Answer
The tally chart can be completed by counting each eye color from the data in Figure 1.
Eye Colour | Tally | Total
------------------------------------
Blue | ||||| (5) | 5
Brown | ||||| || (10) | 10
Green | |||| (4) | 4
Hazel | |||| (4) | 4
------------------------------------
Therefore:
- Total for blue = 5
- Total for brown = 10
- Total for green = 4
- Total for hazel = 4
Step 3
Give another appropriate method of displaying this information.
Answer
Another appropriate method of displaying the information is using a bar graph. A bar graph can visually represent the frequency of each eye color based on the data collected. The x-axis can represent the different eye colors, while the y-axis can represent the total count of individuals for each color.
Step 4
Which sequence is the complementary DNA strand?
Answer
To find the complementary DNA strand, we need to match each base with its complement:
- A (Adenine) pairs with T (Thymine)
- T (Thymine) pairs with A (Adenine)
- G (Guanine) pairs with C (Cytosine)
- C (Cytosine) pairs with G (Guanine)
The given strand is ATGGC TAAGTA, so its complementary strand will be:
TACCG ATTCAT
Thus, the answer is not explicitly listed, but it is derived from the sequence.