Alpha 1 Fetoprotein is a major plasma protein produced by the yolk sac and the liver during fetal life. Alpha fetoprotein expression in adults is often associated with hepatoma or teratoma. However, hereditary persistance of alpha-fetoprotein may also be found in individuals with no obvious pathology. The protein is thought to be the fetal counterpart of serum albumin, and the alpha fetoprotein and albumin genes are present in tandem in the same transcriptional orientation on chromosome 4. Alpha fetoprotein is found in monomeric as well as dimeric and trimeric forms, and binds copper, nickel, fatty acids and bilirubin. The level of alpha fetoprotein in amniotic fluid is used to measure renal loss of protein to screen for spina bifida and anencephaly. Expression has been documented in human adrenal, liver, ovary, testis, and pancreas. ESTs have been isolated from normal human brain, liver/spleen, embryo and uterus tissue libraries.