Diseases Sex Linked And Sex Influenced Essay

Diseases: Sex Linked And Sex Influenced Essay, Research Paper

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 both whole and minced muscle into mice. The minced muscle proved

to be too damaged to operate, and the whole muscle was so large that it died

before an adequate blood and nerve supply was developed. At this point, since

the whole muscle was too large but was the only feasible solution, he decided to

transplant whole muscles of a baby mouse into an adult mouse. This muscle was

not damaged, because it was not minced, and it was not too large, because the

baby muscle is considerably smaller than an adult muscle. Not only did the

mouse survive, but normal function was restored to diseased adult muscle. Since

the transplantation of muscle in mice was so successful, Dr. Law tried to find

something along those lines that would work in a human. He found a solution;

myoblasts. A myoblast is a mature muscle cell. It is a long t

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