Most of the known genetic disorders are dominant gene-linked; however, the vast majority of dominant gene linked disorders are not serious or debilitating. Recessive gene disorders, such as cystic fibrosis and sickle-cell anemia, are less common but may actually claim more lives because they are less likely to be detected as people are unaware that they are carriers of the disease. Some genetic disorders are sex-linked ; the defective gene is found on the X-chromosome. Males have only one X chromosome so are at greater risk for sex-linked disorders due to a recessive gene, such as hemophilia, color-blindness, and baldness.
Human Genetics Problem Set
What causes Tay-Sachs disease? On which chromosome is the HEXA gene? How is Tay-Sachs disease inherited? Is Tay-Sachs disease sex-linked?
Genes and human diseases
Monogenic diseases result from modifications in a single gene occurring in all cells of the body. Though relatively rare, they affect millions of people worldwide. Scientists currently estimate that over 10, of human diseases are known to be monogenic. Pure genetic diseases are caused by a single error in a single gene in the human DNA.
Tay—Sachs disease is a genetic disorder that results in the destruction of nerve cells in the brain and spinal cord. Tay—Sachs disease is caused by a genetic mutation in the HEXA gene on chromosome 15 , which codes for a subunit of the hexosaminidase enzyme known as hexosaminidase A. The treatment of Tay—Sachs disease is supportive in nature. The disease is named after British ophthalmologist Waren Tay , who in first described a symptomatic red spot on the retina of the eye; and American neurologist Bernard Sachs , who described in the cellular changes and noted an increased rate of disease in Ashkenazi Jews. Tay—Sachs disease is typically first noticed in infants around 6 months old displaying an abnormally strong response to sudden noises or other stimuli, known as the "startle response".