And so instead of converting the phenolalanine into tyrosine, what our body will do is it will convert the phenylalanine into toxic substances. And as a result, over time, the accumulation and the build up of the toxic substances will damage the central nervous system and that will lead to many different types of mental abnormalities and mental disabilities. So this is what we mean by pheno keto Neuria. It's one example of a human autosomal recessive disease. Now let's move on to sickle cell anemia. Now, in sickle cell anemia, the individual once again is homozygous recessive.