Chromosome 11

Chromosome 11 is one of the 23 pairs of chromosomes in humans. People normally have two copies of this chromosome. Chromosome 11 spans about 134 million base pairs (the building material of DNA) and represents between 4 and 4.5 percent of the total DNA in cells. Identifying genes on each chromosome is an active area of genetic research. Chromosome 11 likely contains between 1,300 and 1,700 genes. Genes on chromosome 11 are among the estimated 25,000 total genes in the human genome. There are many conditions related to genes on chromosome 11 including Charcot-Marie-Tooth Disease, Alexander Disease, Omenn's Syndrome, Spinocerebellar Ataxia, Aniridia, Denys-Drash Syndrome, Sickle cell anemia, Keratitis, Albinism, and Ewing's Sarcoma (King, 2006).

Charcot-Marie-Tooth disease is a hereditary disorder marked by slowly progressive muscle weakness mostly in the feet and legs, but sometimes in the hands and arms. The weakness results from the degeneration of nerves that stimulate muscle. The disorder is named after three physicians who first identified it in 1886: Jean-Martin Charcot, Pierre Marie, and Howard Tooth. The first symptoms of this disease are usually foot deformities like high arch and flexed toes and difficulty in walking. There is also a tendency to sprain ankles and some difficulty in maintaining balance while standing. It is only necessary for one parent to carry the defective gene for the disease to be transmitted. Male and female children are equally affected. Both electromyography, which is a test measuring the electrical activity of muscle cells, and muscle biopsy tests help diagnosis this disease. There is no known cure for Charcot-Marie-Tooth disease. However, foot deformities can be treated with carefully fitted shoes and proper foot care and regular program of exercise can build up muscles (Torchia, 2005).

Alexander disease is a rare, genetic disorder of the nervous system. It belongs to a group of genetic disorders called the leukodystrophies that affect growth of the myelin sheath, the fatty covering on nerve fibers in the brain. Alexander disease, which affects mostly males, usually begins at about 6 months of age. Symptoms may include mental and physical retardation, memory loss, enlargement of the brain and head, stiffness of arms and legs, and seizures. Other symptoms include failure to grow and gain weight at the expected rate and delays on the development of certain physical, mental, and behavioral skills. There is no cure for Alexander disease, nor is there a standard course of treatment. Most children with this disease do not survive past the age of 6. In most cases, Alexander Disease appears to occur randomly for unknown reasons with no family history of the disease (Robertson, 1999).

Omenn's Syndrome is a rare, inherited disorder of the immune system. It specifically affects three types of cells in our immune system: B lymphocytes and T lymphocytes. Both of these cells plays an important role in fighting infection. Omenn's Syndrome is estimated to occur 1 in 75,000 births. Equal numbers of boys and girls have been diagnosed with Omenn's Syndrome and it appears to be more common in people of North American or European descent. Children with this disease suffer ear infections, failure to thrive, swollen lymph nodes, enlarged liver and spleen, diarrhea, and possibly a skin rash. Infants with this disease are frequently sick and become ill with bacteria and viruses that unaffected babies easily fight off before showing symptoms of an infection. In order for a child to develop this condition, he or she must inherit a copy of the same gene from each parent. Making the diagnosis of Omenn's syndrome requires early recognition of the characteristic signs and symptoms of immune deficiency. Frequent infections, poor growth, and a persistent, generalized rash are warning signs. While there is no known cure for Omenn's syndrome, bone marrow transplantation has been performed to replace the ineffective immune system (Johnston 1999).

Spinocerebellar ataxia (SCA) is a genetic disease with multiple types causing degeneration of the spinal cord and the cerbellum. The cerebellum is concerned with coordination of movements, so losing it results in a loss of muscle coordination. Atrophy in the spine can bring spasms. Like other forms of ataxia, SCA results in unsteady and clumsy motion of the body due to a failure of the fine coordination of muscle movements, along with other symptoms.There is no known cure for this condition, which lasts for the remainder of the sufferer's life. A person with this disease will usually end up needing to use a wheelchair and eventually they will need assistance to perform daily tasks. One way of identifying the disease is with an MRI to view the brain. Once the disease has progressed, the cerebellum in the brain can be seen to have visibly shrunk. The most precise way of identifying this disease is through DNA analysis beacuse some types of spinocerebellar ataxia may be inherited (Wales, 2006).

Aniridia is a rare genetic eye condition causing incomplete formation of the iris. It is present at birth. It is associated with poor development of the retina at the back of the eye, and this causes loss of vision in both eyes. People who have aniridia have enormous pupils. The enormous pupil is often called a 'black iris'. Aniridia literally means "without iris." Aniridia is inherited from parents. Aniridia is caused when the gene responsible for eye development, the PAX6 gene, does not function correctly. Unfortunately, aniridia cannot be treated. The iris functions to restrict the amount of light entering the eye, so if it is absent, most individuals with aniridia are sensitive to bright light. To protect their eyes, tinted glasses or contact lens with artificial iris painted onto them are used (Sorin, 2000).

Denys-Drash syndrome is a very rare disorder that begins early. The syndrome has three main components to it: kidney disease present at birth, Wilms Tumor (a type of kidney cancer), and malformation of the sexual organs. Denys-Drash syndrome predominantly affects infants. Infants with the syndrome are diagnosed with kidney disease between 2 weeks and 18 months of age. The kidney tissue becomes hardened and scarred, which causes nephrotic syndrome. Over time, their kidneys will shut down and stop functioning, which then requires a kidney transplant or dialysis. The Wilms tumor is cancerous and grows on the kidneys, almost all children who have Denys-Drash syndrome will develop this tumor. Sexual organs may also be malformed and under or over developed in some areas. Symptoms of the syndrome include swelling of body parts (especially the abdomen), very little urination, protein in the urine, and high blood pressure. Surgery is the main means of treatment for Denys-Drash syndrome. Both diseased kidneys are removed, as well