I’m trying to study but I’m struggling with simplifying this concept and with understanding it. I’ve never been that good at biology so I’m sorry if it’s a dumb question. It’s a semi-conservative process, because a new strand forms after a cell divides. And this, I have no issue with understanding. But if the 3’-5’ strand is the leading strand (because this is what our teacher has told us) and the DNA polymerase synthesises in the 5’-3’ direction, what about the 5’-3’ strand of the original cell? Our book shows a picture of a recently formed 3’-5’ strand. Does this mean the 5’-3’ strand can also be the leading strand? Sorry I’m just so confused and I think this is crucial to understanding the rest 😭
In: Biology
The 5′ and 3′ refer to the [numbered carbon atoms of the sugar backbone](https://qph.cf2.quoracdn.net/main-qimg-776b674ddbd0bc7b1b2c6902736906a2-pjlq) (deoxyribose in DNA, ribose in RNA).
The important part is that a new nucleotide can only be attached at the 3′ carbon of an existing one. For the 5′-3′ strand this is fine, it can be continuously built forward. The other strand cannot, so instead it is built backward with small steps at a time in its own 5′-3′ direction. These small steps are called [Okazaki fragments](https://en.wikipedia.org/wiki/Okazaki_fragments), and I think looking into these will help.
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