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 derived from the 1 dd out of 4 total genotypes in the Punnett square.

All the children will have the genotype Dd, meaning they will be heterozygous. They inherit one recessive allele (d) from their father and one dominant allele (D) from their mother. Since sickle cell disease is a recessive condition, none of their children will express sickle cell disease as they do not have two copies of the recessive allele (dd).

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

• Cross breed Brahman cattle, which survive well in high temperatures, with Shorthorn cattle, which have good meat quality.
• Select the offspring that exhibit both desirable traits of high temperature survival and good meat quality for further breeding.
• Repeat this process over many generations to enhance these traits in the resulting cattle.

1. Wheat plants that are resistant to fungal disease will not be damaged, leading to higher yields.
2. The spread of the fungus would be reduced, resulting in lower costs for fungicides or pesticides and greater profit margins for farmers.