5' capping--need more clarification

I was a little confused still about 5' capping so did a little further research on it. I still need a little clarification, since this and other sources I found say that a guanosine molecule is methylated on the 5' end and I have in my notes that it is an Adenosine…which is right??
Here is the link to the best information I found about 5' capping…


I also found sources that says there are 7-methylguanosine, thanks for the inquiry. We are all learning.


"During translation, mRNA chains are read in one direction due to the nature of their building blocks, called nucleotides, starting with the 5-prime end, and ending with the 3-prime end. As mRNA chains are synthesized, a 7-methylguanosine cap is attached to the 5-prime end and a tail of repeating adenosine molecules to the 3-prime end. The cap and the tail protect the mRNA from enzymes that would otherwise destroy it from both ends."


** "7-methylguanosine" does not mean that there are actually SEVEN methyl-guanosine molecules…it means that there is one methyl group attached the the 7th carbon in the chain…

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