WASHINGTON, April 11: Moves toward human cloning have been setback by new research released Friday which said experts had identified the reason that attempts to clone primates have failed in the earliest stage of embryo cell division.

“The chromosomes do not split properly. From the very first cell division, development is inappropriate in vital ways,” Gerald Schatten, head of the research group at Pittsburgh University, said in a statement.

“Current techniques such as those used to create Dolly the sheep, mice and other domestic animals do not work in non-human primates,” said Shatten’s colleague Calvin Simley.

To date, five mammalian species — sheep, mice, rabbits, pigs and cows — have been successfully cloned, but numerous attempts with achieve similar results with primates have ended in failure.

By studying what went wrong in more than 700 attempts to make cloned primate embryos, Schatten’s team determined that although imaging of the DNA and basic cell structure gave the impression that cell division, or mitosis, was taking place normally, in fact chromosomal problems existed within each cell.

Research focussed on the “miotic spindles” - thread like guiding structures which in normal cell work to ensure that as mitosis takes place, the chromosomes divide and align indentically.

But in the cloning experiments, the miotic spindles did not form correctly, meaning that the chromosomes did not divide equally and leaving the embryo with an incorrect number of chromosomes.—AFP