One of the most important applications of genotype knowledge in Nigeria is understanding compatibility — specifically, what happens when two people with certain genotypes have children together. This is not just a medical question. It is one of the most consequential decisions a young person will make, and it is far better to understand it now than to discover it after a relationship has deepened. Here is how genotype inheritance works in practice. Each parent passes one copy of their haemoglobin gene to each child. The child inherits one gene from their mother and one from their father. When you know both parents' genotypes, you can work out the probability of each possible outcome for their children. AA and AA: All children will be AA. No risk of sickle cell disease. Fully compatible. AA and AS: Children can be either AA or AS — a 50% chance of each. No children will have SS. Compatible, though children should still know their genotype. AA and SS: All children will be AS. No children will have SS. They will all be carriers, but will not have the disease themselves. AS and AS: This is where significant risk begins. Each pregnancy has a 25% chance of producing an SS child, a 50% chance of AS, and a 25% chance of AA. The 1-in-4 odds sound manageable until you consider that sickle cell disease is a lifelong condition involving chronic pain, frequent hospitalisations, and shortened life expectancy. AS and SS: Each pregnancy has a 50% chance of producing an SS child and 50% AS. These are serious odds. SS and SS: Every child will have sickle cell disease. None of this is about judgement. It is about information. Knowing your genotype — and that of a person you plan to build a life with — gives both of you the facts you need to make informed decisions. Avoiding these conversations does not change the biology. It only removes your agency over it.