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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 determine the offspring's phenotype from a female with blue eyes (bb) and a male with brown eyes (Bb), we create a Punnett square:
B b
----------------
| Bb | bb |
---------------------
| Bb | bb |
The possible genotypes for the child are Bb (brown eyes) and bb (blue eyes). Therefore, the phenotype of the child is brown eyes, as brown is dominant.
Step 2
Complete the tally chart, in Figure 2, for this data.
Answer
To complete the tally chart for the eye colour data:
- Count the occurrences of each eye colour from Figure 1:
- Blue: 10
- Brown: 10
- Green: 4
- Hazel: 6
The completed tally chart will look like this:
eye colour
blue 10
brown 10
green 4
hazel 6
Step 3
Step 4
Which sequence is the complementary DNA strand?
Answer
To determine the complementary DNA strand for the given sequence ATGGCCTAAGTA, we follow the base pairing rules:
- A pairs with T
- T pairs with A
- G pairs with C
- C pairs with G
Thus, the complementary strand is TACCGGATTCA. Looking at the options provided, we find that this corresponds to option B: CGTTAGCCTGC.