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From what I gather, the vast majority (but not all) of the DNA in our genomes will transcribe and create an RNA, if only under certain conditions in a lab (forcibly unwound, among other steps).

How much of our DNA can be transcribed but not translated?

How much actually does so on a regular basis in our cells, becoming useful RNA, but doesn't code a single amino acid? (Non-coding functional RNA, or junk RNA?)

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While, as you say, most of our DNA can be transcribed, you are right that it is not well accessible and/or lacks strong promoters. It's said that over 80% of DNA is transcribed but only <2% transcribes into mRNA, that will be translated [1]. It is not yet known what percentage of non-coding RNA (ncRNA) is junk (by identity) [2], but if weighted by mass or numbers, most of ncRNA is functional as ribosomes and tRNAs make up most of the cells dry mass:

https://www.frontiersin.org/articles/10.3389/fgene.2015.00002/full (image source)

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    $\begingroup$ Minor detail: doesn‘t the left pie chart say that rRNAs make up most of a cell‘s dry mass and not tRNAs..? $\endgroup$
    – markur
    Commented Oct 28, 2022 at 22:53
  • $\begingroup$ I once read in a book „Numbers in Biology“, that ribosomes can make up to 80% of cells dry mass. The chart is not about dry mass but about RNA mass, ignoring not only water but also lipids, proteins etc. $\endgroup$
    – KaPy3141
    Commented Oct 30, 2022 at 8:50
  • $\begingroup$ Oh I meant together they make up most of the cells mass. Not tRNA alone. $\endgroup$
    – KaPy3141
    Commented Oct 30, 2022 at 8:50

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