Other epigenetic processes appear to occur randomly, while others are normal, such as those that guide embryoniccells as they become heart, brain, or liver cells, for example.
Campaigners hope the developed embryoniccells can repair damaged tissues and cure diseases.
支持者希望发达胚胎细胞能修复受损组织并治愈疾病。
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The Salk scientists focused on a biological "priming" system that keeps embryoniccells ready to become whatever kind of tissue they are destined to be.