Diseases: Sex Linked and Sex Influenced

Topics: Muscle, Muscular dystrophy, Color blindness Pages: 8 (3093 words) Published: October 8, 1999
Diseases: Sex Linked and Sex Influenced

by Richard Nixon
Honors Biology
Mrs. Linda
December 19, 1994

There are thousands of cases of sex linked and sex influenced diseases worldwide. These diseases can range from a social inconvenience, to a fatal ailment. In sex linked diseases, like Muscular Dystrophy, hemophilia and color blindness, only males are affected. When a man infected with a sex linked disease has children, all his sons are normal, but all of his daughters are carriers. When a carrier woman and an uninfected man have children, half of the sons are normal, and half of the sons are affected; half of the daughters are carriers and half of the daughters are normal. Only males are affected because the sex linked diseases affect the X chromosome. Males have one X chromosome and one Y chromosome, so they need to use that X, whether it is flawed or not. Females on the other hand, have two X chromosomes, so if one is defective, they can use their second X chromosome. Duchenne's Muscular Dystrophy(DMD) is defined as "a genetic disease characterized by defective muscle cells that can not produce a protein called dystrophins (Science News 380). In patients of hemophilia, there is a deficiency of a protein needed for blood clotting, causing this hereditary bleeding disorder. In red/green color blindness, the broadest form of color blindness that affects six percent of the population, the cones in the retina that receive green light do not function properly. Unlike sex linked diseases, sex influenced diseases are not reserved solely for the male. However, the diseases occur in males much more frequently than in females. This is because sex influenced diseases occur from imbalances in testosterone, much more highly concentrated in males. Baldness and gout are two diseases that are a result of these hormonal imbalances. Baldness is defined as the lack or loss of hair. Permanent baldness strikes on a hereditary basis because the hormonal imbalances tend to be passed from generation to generation. Gout is a hereditary metabolic disorder that involves recurrent acute attacks of severe inflamm ation of joints.

Sex linked diseases are born when sex genes, that compose two of the 46 chromosomes, are mutated by an error in copying genes in reproduction. One of these sex linked diseases is Duchenne's Muscular Dystrophy. DMD is a disease that has rightfully been gaining some headlines recently, as the disease is taking the lives of young children. Several cures have been brought up recently in the medical society, but none have paid any dividends. According to the Muscular Dystrophy Association, one in every 2500 boys are infected with muscular dystrophy. The defective gene is found at the top of the X chromosome. This gene is the largest known to exist. In patients of DMD, this gene is either missing or severely mutilated. The symptoms of DMD are fatal. By age eleven, the victims weaken fast. Normally, muscle deterioration begins in the lower legs and then moves up the body of the patient. Generally, victims are in their early twenties when they die from either heart failure or diaphragm failure.(The diaphragm is the muscle that makes breathing possible.) One mother of a Duchenne's Muscular Dystrophy patient says succinctly, "Eventually these kids get bedridden and then they die."(Grady 87) It is imperative to find a cure for Duchenne's Muscular Dystrophy so we can save the lives of thousands of innocent children.

One of the major researchers working on a cure for DMD is Dr. Peter K. Law of the Cell Therapy Research Foundation. Law has been in the field for over twenty years and has made many discoveries. In 1972, Law's doctoral thesis proved that dystrophic muscle cells have abnormal cell membranes. This showed that the disease was caused by a muscle defect, not a nerve defect as was previously thought. Since it was clear that it was a muscle defect, Law tried to transplant...

Cited: "Color Blindness Misconceptions." USA Today 120 (1992):16 "Foot Feat:
transplant treats dystrophy." Science News 16 June 1990:380 Grady, Denise.
"One foot forward." Discover September 1990:86-93 Massie, Robert., and Massie,
Suzanne. Journey. New York: Alfred A. Knopf, 1961. Norton, Peter B.
"baldness." The New Encyclopedia Britannica. 1994 ed. Norton, Peter B. "gout."
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New Encyclopedia Britannica. 1994 ed. Thompson, Larry. "Cell transplant results
under fire." Science 257 (24 July 1992) 472-474
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