TRANSGENESIS AND USE OF BOUNDARY ELEMENTS WHICH PROTECT AGAINST POSITION EFFECTS

Transgenesis has been frequently used to investigate genetic regulatio n in eucaryotes. This approach provides the opportunity to study gene expression in the whole organism and during development. However, the major drawback of this technique relies on the position effects due to genomic sequences flanking the transgene. Recent studies have allowed boundary sequences to be identified and characterized from Drosophila , chicken and human genomes. When tested by transgenesis in Dlasophila , boundary sequences insulate the transgene from the influence of the surrounding genome. Some of them prevent Integrated DNA from position effects in transformed cells. Although structurally different from eac h other, they seem to have conserved some insulating properties throug h evolution. Their study may provide new information concerning gene r egulation by higher order chromatin packaging.