It's phosphate, carbon, carbon, carbon, phosphate, carbon, carbon, carbon, phosphate and it has this structure hanging off the side.

就是磷酸基与戊糖的碳反复连接,如此循环往复,这种结构构成了主链的一边

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It wouldn't be the same if I turned it upside down because the carbons - the rings here, the pentose's would all be turned over, the chemistry would look different and the sequence of bases would look different.

记住单链倒过来,就和原来不一样了,这是因为碳原子和糖环结构,戊糖会翻转,使得这个化学结构看起来不一样了,碱基的顺序也不一样了

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