This represents the upright struts on a ladder that I showed you before, it represents this backbone that's shown by - that's formed by polymerizing the pentose's together through phosphate's always going 5' to 3', 5' to 3'.

线条代表梯子,上下的支柱 之前给你们演示过,代表由多聚戊糖分子,通过磷酸基从5'端向3'端方向,连接起来的主链

耶鲁公开课 - 生物医学工程探索课程节选

The backbone's on the outside of the molecule like the upright struts of a ladder on the outside of a ladder.

主链位于DNA分子结构外侧,像梯子两侧上下的支柱,记住是梯子外侧

耶鲁公开课 - 生物医学工程探索课程节选