I am sorry to bother with this question (i study genetics for about few hours, because I need to understand my data) and I am really confused about these two terms, because I dont know if the books uses word "reverse" interchengeably or what is going on here.

The main problem I am totally confused about are words reverse complementarity and complementarity of two DNA strands. Since I know that strands runs in antiparallel directions and two DNA strands are complementary to each other: i.e. sequence ACTCTG is complementary to TGAGAC and vice versa.

But my question is: are two DNA strands reverse complementary to each other? Because at least in two books I have read that two strands of DNA are. But if I would apply it to my previous example and use reversion, then no way I can get to my other strand. Is the word reverse in this context use as antiparalel (5' - 3' and 3' - 5') or am I missing something and it's true that if I take the whole DNA strand, I can use complement and reverse it and it will be my other strand?

Again I am sorry to ask this really basic question, but I am so confused about this terms. Nice day to all and thanks if someone will have time to answer my question.

  • 1
    $\begingroup$ There is already a comprehensive answer to a previous question of which this is essentially a duplicate. $\endgroup$
    – David
    Mar 1, 2021 at 17:28

1 Answer 1


I agree that the definitions can be somewhat confusing when first encountered. Each nucleotide has a complement A-T, C-G. But the DNA strand are reverse-complementary because when aligned from 5'->3' they are not (necessarily) complementary.
For example:
DNA strand 5'-ATCCGG-3'
complement 3'-TAGGCC-5'
reverse 5'-CCGGAT-3'

Since we want to write all sequences in the same direction we must call the strand reverse-complementary

  • 1
    $\begingroup$ OK, thank you a lot. I did not realise that there is a convention to align two strands of DNA in the same direction and then speaking of reverse complementarity. But it seems like a pretty natural way for comparing. Thank a lot again, and have a nice day! $\endgroup$
    – stanly
    Feb 27, 2021 at 22:45

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