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In the initiation of DNA synthesis:

the RNA segments are first synthesized by primase and then elongated by DNA polymerase (Wikipedia).

What does 'elongated' mean in this context? Is it possible for RNA and DNA to form a phosphodiester bond to make a single strand which is part RNA and then part DNA?

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  • $\begingroup$ A biochemistry book, such as Berg et al. online, is far better than Wikipedia. Your question is answered in section 27.4.1 — see Figure 27.26. Try other books on the NCBI Bookshelf searching for Okazaki fragments. $\endgroup$ – David Oct 19 '17 at 11:03
  • $\begingroup$ @David thank you very much David , I've read the section 27.4.1 and the figure 27.26 but a bit unsure about it. It mean that a RNA and DNA can forms a sugar backbone bond between them to make a single strand RNA-DNA ?. I used to think that the RNA cannot forming bond with DNA like that and I was wrong. Thank you again! $\endgroup$ – joe Oct 19 '17 at 14:50
  • $\begingroup$ The problem is not forming a phosphodiester bond between ribose and deoxyribose (chemically the same) but that one would expect a DNA polymerase to discriminate against the 3'OH of the ribose. You are in good company being surprised that it happens — it was an unexpected discovery at the time. I suspect that some component of the DNA polymerization process confers this changed specificity, but it is not my field and I haven't time to check this. If anyone knows the details I suggest they formulate them into a more comprehensive answer. $\endgroup$ – David Oct 20 '17 at 6:46

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