| |
|
 |
Scientists
have found a G-protein defect in one type of inherited
night blindness. Persons with this condition have a mutation
in the gene
that codes for the G-protein
found in the eye's rod cells.
Scientists believe that this defective G-protein is overactive. It
stays turned on more than it normally would, and the person can't
see well at low light levels.
During the day, a similar system in the cone cells of the eyes allows
us to see color. This system depends on a different G-protein. Thus,
persons with night blindness have normal daytime vision.
 |
|
Light
enters the eye (1) and strikes the rod cells in the retina
(2). Light receptors, G-proteins and amplifiers are on discs
within
the rods (3).
When light strikes a light receptor, it activates a G-protein,
which binds to an amplifier molecule. This sends a signal to
the brain, resulting in light perception. G-proteins normally
turn themselves off in a natural regulatory cycle. But in inherited
night blindness, the G-protein stays on, interfering with normal
vision. |
|
Image: Courtesy
of NIDDK
For Section 508 Handicap Accessibility, please visit our Text
Only site.
|
| |
|
