The diagram shows two red blood cells - Edexcel - GCSE Biology - Question 4 - 2018 - Paper 1
Question 4
The diagram shows two red blood cells.
One is affected by sickle cell disease and the other is not.
Worked Solution & Example Answer:The diagram shows two red blood cells - Edexcel - GCSE Biology - Question 4 - 2018 - Paper 1
Step 1
An explanation linking three of the following points:
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Answer
Sickle cell disease results in red blood cells that are deformed or sickle-shaped, which reduces the oxygen-carrying capacity of the blood. This shape change leads to less aerobic respiration occurring in the cells, ultimately resulting in less energy being released for bodily functions. Furthermore, sickle-shaped cells can block blood vessels, causing painful joints due to reduced blood flow.
Step 2
genotype
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Answer
The genotype of an individual with sickle cell disease is represented as 'dd', indicating that they are homozygous recessive for the sickle cell trait.
Step 3
recessive
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Answer
The sickle cell trait is recessive, which means that a person must inherit two copies of the mutated gene to express the disease.
Step 4
Probability Calculation:
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Answer
The probability of having offspring with the genotype 'dd' (sickle cell disease) from the given parental genotypes (Dd x Dd) is 25%. This is calculated using a Punnett Square, which shows that out of four possible combinations, only one results in 'dd'.
Step 5
An explanation linking the following points:
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Answer
Sickle cell disease can cause build-up of thick or sticky mucus in the body, which traps more bacteria, increasing the likelihood of infections.
