A neural tube defect characterized by absence of the forebrain, front part of the skull and overlying skin. Affected infants are stillborn or die within hours of delivery. Can occur in families with spina bifida, but the mode of inheritance is not understood. Neural tube defects can be diagnosed during pregnancy. Although the condition can run in families, the responsible genes have not yet been identified.
Bipolar disorder is probably due to the interaction of many different genes.
But the genetics of most cancers are not well understood. May be due to chromosomal rearrangements, mutation in individual genes, to environmental insult, or to combinations of factors. Some forms are attributable to environmental insult such as thalidomide ingested during pregnancy. This causes ambiguous external genitalia in females. A more severe form of the disease causes salt loss and can lead to death in newborn infants.