A team of scientists led by Teruhiko Wakayama at Yamanashi University in Japan has successfully transferred a chromosome from a rat that had been frozen for over a year into living mouse cells, creating chimeric mice with some cells containing the added chromosome. This breakthrough could significantly advance de-extinction efforts, particularly for species like the Hawaiian poʻouli bird that requires chromosome transfer for revival. The researchers aim to refine their technique further and apply it to elephant cells, potentially leading to the introduction of mammoth chromosomes into living cells. The process involves injecting a cell's nucleus into an egg to trigger chromosome condensation, followed by the extraction and injection of a single chromosome into another egg. While the current technique works only with rat chromosome 9, the team is exploring methods to improve success rates. The research opens new avenues for studying genes from extinct species, which could enhance conservation strategies and provide insights into genetic activity.