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 (dd) can be calculated. Since there is 1 dd out of 4 total genotypes, the probability is:

$\frac{1}{4} \times 100 \% = 25 \%$

Thus, the answer is:

percentage probability = 25 %

The father has the genotype dd, which means he expresses sickle cell disease, while the mother is DD and does not. When they have children, all offspring will inherit one allele from each parent:

• Each child will inherit a dominant D allele from the mother.
• All children will therefore have the genotype Dd (heterozygous) and will not exhibit sickle cell disease since it requires two recessive alleles (dd) to express the condition.

To selectively breed cattle for high survival in hot temperatures and good meat quality, one could:

• Cross breed Brahman cattle, which are good at surviving high temperatures, with Shorthorn cattle, known for meat quality. This will combine the desirable traits.
• After hybridization, select the offspring that exhibit both desired characteristics.
• Repeat over many generations, ensuring that only the offspring with both traits are used for further breeding.

Breeding wheat plants that are resistant to fungal disease has several benefits:

1. Wheat plants not damaged by the fungus will thrive better, leading to higher yields.
2. The spread of the fungus would be reduced, minimizing the risk of crop loss and improving overall agricultural sustainability.