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The Human Eye
See a video of how genes work in the human eye.
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Genes guide the physical development, functions and maintenance of our bodies from the moment we are conceived. All of our senses—sight, touch, taste, smell and hearing—depend on how our genes direct our bodies to interpret stimuli.
In the eye, for example, cone cells contain the cues needed for a person to see colors. A mistake in the genetic code can cause light waves entering the eye to be ignored or misread, resulting in color blindness.
The eye: Where sight begins
Color vision starts when light enters the eye and hits a receptor that signals the brain to recognize different colors—red, green or blue.
Seeing Red and Green
Most people can see the primary colors of a traffic light because of a gene that codes for color vision. But an error in that gene's DNA code causes some viewers to see red and green as shades of yellowish brown. Roughly 10 million men and 550,000 women in the United States are color blind.
Cells
The fundamental microscopic unit of which all living things except viruses are composed
Chromosomes
The structures in a cell’s nucleus that contains DNA; human cells have 46 chromosomes each (23 from each parent).
DNA (deoxyribonucleic acid)
The molecule that encodes genetic information, in the form of a double helix held together by bonds between base pairs.
Genes
The fundamental unit of heredity; a specific sequence of DNA that controls the transmission and expression of one or more hereditary traits by encoding a specific product such as a protein.
Proteins
A large molecule, composed of one or more chains of amino acids in a specific order. Proteins are required for the structure, function, and regulation of an organism’s cells, tissues, and organs, and each protein has unique functions. Examples are hormones, enzymes, and antibodies.
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