Artificial chromosomes: just add genes.

Geneticists working on the Human Genome Project - the worldwide effort to map and decipher all of the genes that make up a human being - are well on their way to constructing an artificial mammalian chromosome, a technical advance that could speed and simplify the herculean endeavor.

Peter N. Goodfellow of the Imperial Cancer Research Fund in London, England, and his colleagues have successfully moved a telomere -- the specialized structure that keeps the tips of chromosomes from unraveling -- up toward the center of the long arm of a mammalian X chromosome. As a result, they have created a chromosome whose long arm consists only of a centromere -- the pinched region that holds the two halves of a chromosome together - and a telomere, with no intervening genes.

"This is the first step for creating mammalian artificial chromosomes," asserts Goodfellow, who recently accepted a new post at the University of Cambridge. He says the artificial chromosome will be complete once his team moves a second telomere up the short arm of the chromosome. The artificial chromosome will consist of only two telomeres joined by a centromere, forming a blank "cassette" into which researchers can insert single human genes for study,

Currently, geneticists must use artificial bacterial and yeast chromosomes to copy and manipulate inserted human genes. But these chromosomes are sometimes too small to contain entire human genes, which often consist of millions of units of DNA.

Artificial mammalian chromosomes would enable geneticists to manipulate human DNA in a way more nearly resembling the action of genes in the body, Goodfellow says. He suggests they might also serve as vehicles for inserting foreign genes into patients during gene therapy for genetic diseases.