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).
The term mosaicism is used to describe the presence of more than one type of cell in a person. For example, a person may have some of the cells in his or her body with 46 chromosomes, while other cells in his or her body have 47 chromosomes. An example of mosaicism is mosaic Down syndrome.