Why is an allele recessive?

A recessive allele means that the person has gotten two types of the same allele from each parent. This explains why there are some children who develop certain conditions even if their parents do not have those conditions. It is because their parents are carriers and they do not know about it.

If there is only one recessive allele that is received from one parent, then it will not manifest through the person but the person will also become a carrier. This recessive allele will then be passed on to the next generation if the person will have children in the future.