Sickle cell disease is a recessive genetic disorder in humans - Edexcel - GCSE Biology Combined Science - Question 2 - 2021 - Paper 1

The percentage probability that their children could have sickle cell disease is 25%. This is because only the genotype dd expresses sickle cell disease, which occurs in 1 out of the 4 possible genotypes.

None of the children will have sickle cell disease because the father has the genotype dd, which is recessive, and the mother has the genotype DD, which is dominant. Since each child will inherit one allele from each parent, the father can only pass on a recessive d, while the mother can only pass on a dominant D, making all offspring heterozygous (Dd), thus unable to express the sickle cell disease.

To produce cattle that can survive high temperatures and have good meat quality, one could:

• Cross Brahman cattle, known for their survival in high temperatures, with Shorthorn cattle, known for their good meat quality.
• Select the offspring with the desired combination of traits and continue to breed them over multiple generations.

1. Wheat plants that are resistant to fungal disease will not be damaged, leading to a healthier crop yield.
2. This breeding could also reduce the use of fungicides/pesticides, which helps in lowering production costs and environmental impact.