One would expect that, with one non- functional gene, the enzyme level in a person's body would be about half normal. It is interesting that carriers often appear normal. This seems to be based upon the phenomenon that half the normal enzyme level is often adequate for good health. Recall that if an individual receives two defective genes from their parents, essentially no active enzyme is produced, leading to the disease. Let us examine the possibilities.
All offspring exhibit normal health One out of four offspring .
The same is true for each sperm. Therefore, in the case of a man and woman who both carry only functional genes, only R eggs and R sperm are produced. This is reflected in this simple table. Therefore, no children of this mating will have the disease. Note the possible children.