Blame it on the genes

Fragile X syndrome:
Mental retardation in men blamed on abnormal recurrence of a DNA sequence.

Huntington's disease:
Malfunction in muscle movement and coordination caused by the high recurrence of a DNA fragment.

Myotonic dystrophy:
Abnormal muscle contraction. It is thought only some cells of affected individuals carry the defective genes.

Kallmann syndrome:
Underdeveloped reproductive organs and impaired sense of smell. Faulty protein coding affects the movement of olfactory nerve cells, which later simulate nerve cells responsible for secreting hormones that control the development of reproductive organs.

Miller-Dieker syndrome:
Retarded brain development caused by the absence of a protein that controls the migration of nerve cells.

Alzheimer's disease:
A progressive degenerative disease of the brain which results in impaired memory, thinking and behaviour. Researchers believe several gene mutations may be responsible for the disease.