Each cell within the human body contains thousands of genes, which collectively make up the genome. The genes are arranged in larger groupings, called chromosomes, and most cells within the human body contain a pair of 23 different chromosomes, for 46 total. Each gene codes for one or more proteins, and each protein has specialized functions within the cell. Genetic mutations, which can include small modifications to single genes; gene deletions; or chromosomal abnormalities can all disrupt essential protein functioning and cause a number of diseases in humans.
Angelman Syndrome
Angelman syndrome affects about one in every 12,000 to 20,000 people, according to the Genetics Home Reference. Angelman syndrome primarily affects the nervous system. Patients with Angelman syndrome experience significant developmental delays and mental retardation, as well as small head size, seizures, craniofacial abnormalities and behavioral problems, such as hyperactivity and difficulty sleeping. Angelman syndrome is associated with genetic mutations that lead to the inactivation or deletion of a gene called UBE3A.
Red-Green Color Blindness
Another genetic disease in humans is red-green color blindness, the inability to distinguish between red and green. Light and color are detected by specialized cells within the eye, called rods and cones, respectively. Cones, the structures responsible for detecting different colors, activate in response to red, green or blue light. Patients with red-green color blindness have cone abnormalities, so the patient cannot distinguish between green and red.
Red-green color blindness is called an X-linked condition, because the disease is associated with a mutation to the X chromosome. The disease is X-linked recessive, which means that all copies of the X chromosome must be mutated for a patient to have the condition. As a result, red-green color blindness is 16 times more common in males, who have only one X chromosome, than females, who have two, reports the MUSC Childrens Hospital.
Canavan Disease
Canavan disease affects the brain and is most common in Ashkenazi Jew populations, reports the University of Maryland Medical Center. Patients with Canavan disease cannot metabolize a substance called aspartic acid; this metabolic process is essential to maintain the health of the brain. The aspartic acid metabolism deficiency stems from mutation to a gene called ASPA, which is normally found in nerve cells. ASPA normally helps break down aspartic acid and helps with the production of a compound called myelin, which facilitates communication between nerve cells in the brain, reports the Genetics Home Reference. In Canavan disease patients with ASPA mutations, the brain cannot break down aspartic acid and cannot produce myelin, and therefore cannot function properly.
The symptoms of Canavan disease begin early in life, and include abnormal posture and poor muscle tone, mental retardation, problems feeding, blindness, and seizures. The disease is progressive and incurable, and can ultimately prove fatal.
