1 in 15,000 infants suffers from this problem. PKU homozygotes are now routinely tested for in most states. If you look closely at a product containing Nutra-sweet artificial sweetener, you will see a warning to PKU sufferers since phenylalanine is one of the amino acids in the sweetener. PKU sufferers are placed on a diet low in phenylalanine, enough for metabolic needs but not enough to cause the buildup of harmful intermediates. Tay-Sachs Disease is an autosomal recessive resulting in degeneration of the nervous system.
Symptoms manifest after birth.
Children homozygous recessive for this allele rarely survive past five years of age. This lipid accumulates in lysosomes in brain cells, eventually killing the brain cells. Sickle-cell anemia is an autosomal recessive we have discussed in other sections. The recessive allele causes a single amino acid substitution in the beta chains of hemoglobin . When oxygen concentration is low, sickling of cells occurs.