Artificial organ almost always preceded by extensive experiments with animals. Initial testing in humans is frequently limited to those either already facing death or who have exhausted every other treatment possibility. Artificial arms and legs, or prosthetics, are intended to restore a degree of normal function to amputees. Mechanical devices that allow amputees to walk again or continue to use two hands have probably been in use since ancient times, the most notable one being the simple peg leg. Since then, the development of artificial limbs has progressed rapidly. New plastics and other materials, such as carbon fiber have allowed artificial limbs
Human artificial chromosome Genetic material was then introduced as mentioned above, using the Cre-Lox recombination system. This particular study focused on changes in expression levels by leaving portions of the existing genomic DNA. By leaving existing telomeric and sub-telomeric sequences, they were able to amplify expression levels of genes coding for erythropoietin production over 1000-fold. This work also has large gene therapy implications, as erythropoietin controls red blood cell formation. HACs have been used to create transgenic animals for use as animal models of human disease and for production of therapeutic products. Human artificial chromosome A human artificial chromosome (HAC) is a microchromosome