But they behave just like the real thing when they're in human cells. They duplicate themselves as the cell gets ready to divide, and each copy passes into one of the resulting cells. The researchers created at least two artificial chromosomes, but it's their technique that will be useful. For example, it will help scientists discover what turns particular genes on and off, Willard said. That's a big question for treating genetic diseases by planting genes in patients, because scientists want the implanted genes to behave normally.
Genes act like loyal citizens of their chromosome neighborhood, taking their cues from neighbors.
For most genes, scientists don't know which neighbors give the cues to turn on or off. But now, scientists will be able to take a large chromosome fragment that contains a gene plus some of its neighbors, turn the fragment into a full chromosome, stick it into human cells and watch how the gene behaves. By experimenting with different fragments that include different neighbors, scientists will be able to pin down what regulates the gene.