Why are certain genes recessive and others dominant?

Answer

The difference between a dominant and a recessive inherited disease is actually determined by the effect of the “error” on the functioning of the protein that is affected.

If this effect, for example, causes the protein to stop working, or only slightly, then the “healthy” protein (on the other chromosome) can normally still compensate and the disease will not occur. Only if there are two “wrong” genes is the disease expressed. In this case, it is therefore a recessively inherited disease.

But if the “wrong” protein, for example, has a different effect, or starts working too hard, or starts behaving strangely, for example by piling up on something, then the disease will also be expressed in people who have only one copy of the “wrong” protein. gene, and then the disease is dominantly inherited.