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
An explanation linking three of the following points:

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- Red blood cells which are deformed or sickle-shaped result from sickle cell disease.
- This alteration reduces the oxygen-carrying capacity of the blood.
- As a consequence of the reduced oxygen capacity, less aerobic respiration occurs.
- Finally, this leads to less energy being released for bodily functions.
genotype

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The complete genetic makeup of an organism; in the case of sickle cell disease, it can be homozygous recessive (dd).
recessive

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A trait that only manifests when an individual has two copies of the recessive allele (e.g., dd).
homozygous

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An organism that has two identical alleles for a trait, such as being homozygous recessive for sickle cell disease.
one mark for offspring genotypes

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The potential offspring genotypes can be explored through a Punnett square, revealing DD, Dd, Dd, and dd.
one mark for correct probability

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The probability of offspring being affected by sickle cell disease (dd) is 25%.
An explanation linking the following points:

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- Sickle cell disease leads to a build-up of thick or sticky mucus in the body.
- This thicker mucus can trap more bacteria, increasing the risk of infections.
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