Genetic Engineering and Human Health

Genetic Disorders

Genetic illnesses are diseases caused by one or more damaged, mutated, or defective genes. These illnesses are extremely difficult to treat because the heart of the problem lies in the genetic code, which will continue to produce the condition unless it is corrected. Because the defective gene or genes for the illness is imbedded in the DNA, treatments have fallen short, only able to target the resulting effects of the disease produced by the ongoing construction of the destructive genetic codes. Finding, targeting, and correcting these genes is the focus, challenge, and hope of genetic engineering.

There are thousands of genetic illnesses: cancer, diabetes, asthma, melanoma, hemophilia, and sickle cell anemia are just a few. Some are genetic diseases are monogenetic, meaning they are caused by a single defective gene while other illness are polygenic, involving more than one defect gene. Other illnesses are caused because a whole chromosome or large segments of the chromosome are missing, duplicated, or damages as in Williams, Turners, and Downs Syndrome. Polygenic illnesses are more difficult to treat because more than one gene is involved. Monogenetic illnesses are cause by a single defective or mutated gene, which alters or eliminates the production of that gene's encoded protein. This one change can have catastrophic effects on human health as seen in diseases such as sickle -cell anemia, cystic fibrosis, Huntington's disease, and hemophilia. ²⁵

Sickle Cell Anemia

Sickle cell anemia is an inherited blood disorder passed on through a single gene. This illness affects the ability of good hemoglobin (HbA) to carry oxygen. This genetic trait is recessive, and therefore can be carried genetically by a parent unnoticed. However, when a child inherits both damaged genes (one from the mother and one from the father), he acquires the illness. Sickle-cell anemia is a monogenetic illness, which means that the illness is cause by only one gene. This one problematic gene in located where the hemoglobin is coded. The defective gene, codon, which should be GAG, is incorrectly coded as GTG. ²⁶ As a result, the ribosome reads GTG and makes the amino acid valine, instead of the correct amino acid glutamic, GAG. This one difference has a catastrophic effect on the ability of the hemoglobin molecule to carry oxygen. As a result, an abnormal form of hemoglobin (HbS) is produced, which is unable to carry the oxygen needed. Healthy red blood cells are flexible, disc-shaped cells that last about 4 month, are able to hold needed oxygen, and move easily through the blood vessels. The fragile sickle cells are sticky, stiff, and fragile resulting in moon-shaped blood cells that clot too easily, and break down after about 10-20 days (instead of the normal 120 days) causing anemia. Gene therapies are being explored to treat sickle cell anemia by replacing or altering the gene that causes it. ²⁷

Cancer

Although there are many different kinds of cancers, these cells have some common characteristics. A cancer cell does not contribute to the function of the body. It does not differentiate itself into a muscle, nerve, or bone cell. Cancer cells have abnormally large nuclei and can have the wrong number of chromosomes from a normal cell. Most importantly, a cancer cell has the ability to replicate without limitation and has been called immortal. ²⁸ An example of the cancer cell's ability to replicate could be noted in the historic story of Henrietta Lacks and the "Hela" cell. This cancerous cell was isolated without permission from a cervical tumor of a young woman named Henrietta Lacks in 1951. This cancer cell replicated prolifically in culture: scientists where having difficulty in finding cells that had this property. This cell was shared among scientists and continued to replicate, eventually contributing profoundly to the advancement of research and medical treatments.

Cancer has many genetic links. The mutated gene, p16 is thought to be associated with melanoma, the gene that codes for telomerase in turned off in normal cells, but active in cancer cells, the inherited gene, BRCA1 is proven to cause breast cancer. The prolific unrestrained replication of cells is a characteristic of most cancers and the advancement of technologies is linking genetic origins. Preventing and treating cancers is the focus of much research, development, and genetic therapy.