A team of researchers at Hannover Medical School, Germany, has found a telomerase-dependent telomere length–resetting event between the morula and blastocyst embryonic stages that they say keeps cloned embryo telomere length normal.

Because telomeres—the structures located at the end of chromosomes—lose a piece of their sequences with each cell division, short telomeres are usually correlated with age, said Heiner Niemann, professor and head of the Department of Biotechnology at the Institut für Tierzucht, Neustadt, Germany, who coauthored the study, published in the May 17 PNAS Early Edition, with Sonja Schaetzlein and colleagues.

Scientists had earlier looked at telomere lengths in cloned animals because there was some concern that such animals may exhibit premature aging. “There was quite an uproar with Dolly [the first sheep clone] in that when they measured telomere length, they were indeed obviously shortened compared to age-matched controls,” Niemann said. However, later studies in...

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