Stalactites have to hang on tight to the ceiling or they might fall off.

VOA: special.2009.12.07

It's a double stranded circular piece of DNA, meaning that the 3', 5'ends that hang off are joined back together again to form a continuous loop.

它是双链环状DNA,它的3'末端和5'末端首尾相连,构成一种连续环状结构

耶鲁公开课 - 生物医学工程探索课程节选

It's a double stranded circular piece of DNA, meaning that the 3', 5'ends that hang off are joined back together again to form a continuous loop.

它是双链环状DNA,它的3'末端和5'末端首尾相连,构成一种连续环状结构

耶鲁公开课 - 生物医学工程探索课程节选