Research To Date Has Shown: 1  ADHD is a neurobiologic condition whose symptoms are also dependent on the child's environment. 2  A lower level of activity in the parts of the brain that control attention and activity level may be associated with ADHD. 3  ADHD frequently runs in families.
Mosaic (genetics) In genetics, a mosaic (or mosaicism) means the presence of two different genotypes in an individual which developed from a single fertilized egg. As a result, the individual has two or more genetically different cell lines derived from a single zygote. Unusual events in cell division (mitosis).
noun, Biology. 1. a condition in which an organism or part is composed of two or more genetically distinct tissues owing to experimental manipulation or to faulty distribution of genetic material during mitosis. Origin of mosaicism.