Photo AI
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 phenotype of the child, we use a Punnett square with the alleles of both parents. The woman has blue eyes, which is represented as 'bb', while the man has brown eyes but can be either 'BB' or 'Bb'. Since the man has brown eyes, we assume he is 'Bb' for this Punnett square.
Here is the completed Punnett square:
| B | B |
-------------------------
b | Bb | Bb |
-------------------------
b | Bb | Bb |
From this Punnett square, we can see that 100% of the offspring will have at least one 'B' allele, resulting in a phenotype of brown eyes.
Step 2
Complete the tally chart, in Figure 2, for this data.
Answer
To complete the tally chart for the 30 people's eye colours, we count each colour from Figure 1:
- Blue: 10
- Brown: 12
- Green: 4
- Hazel: 4
The completed tally chart in Figure 2 will look as follows:
eye colour | tally | total
-----------------------------------
blue | |||||||||| | 10
brown | |||||||||||| | 12
green | |||| | 4
hazel | |||| | 4
-----------------------------------
Total | 30
Step 3
Give another appropriate method of displaying this information.
Answer
Another appropriate method of displaying this information is through a bar chart, where each eye colour is represented by a bar. The height of each bar corresponds to the number of individuals having that eye colour. For example:
- Blue: 10
- Brown: 12
- Green: 4
- Hazel: 4
This visual representation makes it easier to compare the frequencies of each eye colour.
Step 4
Which sequence is the complementary DNA strand?
Answer
To find the complementary DNA strand for the given sequence 'ATGGCTAAGTA', we pair the bases according to the rule (A-T, G-C):
- A pairs with T
- T pairs with A
- G pairs with C
- C pairs with G
Thus, the complementary strand is 'TACCGATTCAT'. Looking at the options:
A - ATGGCTAAGTA B - CGTTAGCCTGC C - TACCGATTCAT D - GCAATGACGC
The correct answer is C: TACCGATTCAT.