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10 (a) The UK driving test requires a person to be able to read a number plate at a distance of 20.5 metres - Edexcel - GCSE Biology - Question 10 - 2020 - Paper 1
Question 10
10 (a) The UK driving test requires a person to be able to read a number plate at a distance of 20.5 metres. Some people are short-sighted so cannot read the number... show full transcript
Worked Solution & Example Answer:10 (a) The UK driving test requires a person to be able to read a number plate at a distance of 20.5 metres - Edexcel - GCSE Biology - Question 10 - 2020 - Paper 1
Step 1
Explain how a diverging lens corrects short-sightedness.
Answer
A diverging lens, also known as a concave lens, helps individuals who are short-sighted by diverging light rays before they enter the eye. This means that light rays are spread out, allowing the image to be focused directly onto the retina, rather than in front of it. This correction ensures that distant objects appear clearer.
Step 2
What is the number of men who are colour blind in the city?
Answer
To calculate the number of men who are colour blind in the city:
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Determine the number of men in the city:
- Total population = 2,000,000
- Percentage of men = 51%
- Number of men = 2,000,000 * 0.51 = 1,020,000
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Calculate the number of men who are colour blind:
- Colour blindness affects 1 in 12 men:
- Number of colour blind men = 1,020,000 / 12 ≈ 85,000.
Thus, the answer is B 85 000.
Step 3
Explain why more men than women are colour blind.
Answer
Colour blindness is linked to the X chromosome, and since men have only one X chromosome (XY), if they inherit the affected allele, they will express colour blindness. Women, however, have two X chromosomes (XX), meaning they would require two copies of the affected allele to express the condition, making it less common in females. Therefore, more men are colour blind compared to women.
Step 4
Explain the probability of the baby boy being colour blind.
Answer
In this scenario:
- The father is colour blind, meaning he has the affected allele on his X chromosome (X^cY).
- The mother does not carry the allele (XX).
When they have a baby boy, the boy receives the Y chromosome from his father and one X chromosome from his mother. The mother can only pass on a normal X chromosome (X). Therefore, the baby boy will inherit the combination XY (where X is normal) and will not be colour blind. Thus, the probability of the baby boy being colour blind is 0%.
Step 5
Explain how a change in the DNA sequence of a gene can result in the production of a different protein.
Answer
Changes in the DNA sequence of a gene can lead to the production of a different mRNA sequence during transcription. This altered mRNA may code for a different amino acid in the resulting protein. As proteins are composed of chains of amino acids, a different amino acid can change the structure of the protein. This change can affect how the protein folds and its overall function, which, in the context of colour blindness, may lead to the production of a protein that does not function properly in color detection.