Domingo Liotta and Surgery in 1953. In 1955, he developed a technique for early diagnosis of tumors in the pancreas and ampulla of Vater (Pour le diagnostic des tumeurs du pancreas: La duodenographie hypotonique. Lyon Chirurgical, 1955). Liotta continued his medical career at the University of Lyon (France) at the "Pierre Mallet-Guy's" General Surgery Service. Then, he trained in thoracic and cardiac surgery, with Professors Paul Santy and Pierre Marion in Lyon France. His early works in the artificial heart are from 1958 in Córdoba, Argentina, where he developed an early prototype successfully used in small animals. After publishing the results of
Human artificial chromosome by these vectors not only leads to different expression levels, but the inserts also disrupt the original genome. HACs differ in this regard, as they are entirely separate chromosomes. This separation from existing genetic material assumes that no insertional mutants would arise. This stability and accuracy makes HACs preferable to other methods such as viral vectors, YACs and BACs. HACs allow for delivery of more DNA (including promoters and copy-number variation) than is possible with viral vectors. Yeast artificial chromosomes and bacterial artificial chromosomes were created before human artificial chromosomes, which first appeared in 1997. HACs are useful in expression