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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
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 plate ... show full transcript
Worked Solution & Example Answer: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 is used to correct short-sightedness by adjusting the path of light rays entering the eye. In individuals with short-sightedness, the eye is typically longer than normal, causing light rays to focus in front of the retina. The diverging lens scatters the light rays, enabling them to diverge slightly before reaching the eye, thus allowing the rays to focus correctly on the retina.
Step 2
What is the number of men who are colour blind in the city?
Answer
To determine the number of men who are colour blind in the city, we first find the total number of men. In a city of 2 million people, with 51% being men, the calculation is:
Next, since colour blindness affects 1 in 12 men, the number of colour blind men is:
ext{Colour blind men} = rac{1,020,000}{12} = 85,000
Thus, the number of men who are colour blind in the city is 85,000.
Step 3
Explain why more men than women are colour blind.
Answer
The reason why more men than women are colour blind is due to the genetic location of the allele responsible for the condition. Colour blindness is a sex-linked trait associated with a recessive allele found on the X chromosome. Since men have one X chromosome (XY), if they inherit the allele for colour blindness, they will express the trait. In contrast, women have two X chromosomes (XX), so for a woman to be colour blind, she must inherit two copies of the recessive allele. This biological difference results in a higher prevalence of colour blindness in men.
Step 4
Explain the probability of the baby boy being colour blind.
Answer
In this scenario, the mother does not have the allele for colour blindness, which indicates her genotype is XX (normal vision). The father is colour blind, implying his genotype is X^cY (where X^c represents the allele for colour blindness).
When the mother has a son, he will inherit one X chromosome from her and one Y chromosome from the father. Since the mother contributes a normal X chromosome, the son will have the genotype XY.
Thus, the probability of this baby boy being colour blind is 0 because he cannot inherit the allele from his mother.
Step 5
Explain how a change in the DNA sequence of a gene can result in the production of a different protein.
Answer
A change in the DNA sequence, known as a mutation, can lead to the production of a different protein by altering the corresponding mRNA sequence during transcription. When the DNA sequence is transcribed, it creates a messenger RNA (mRNA) copy of that sequence. The mRNA serves as a template for protein synthesis during translation. If there is a change in the DNA sequence, it can lead to a different sequence of amino acids being assembled in the protein. This change could result in a protein that has a different structure and function, potentially affecting its role in the body.