Read the other strand.

Reverse complement, complement or reverse?

A reverse complement applies base pairing and reverses the order of the input. For a DNA sequence entered 5′ to 3′, the result is the opposite strand written 5′ to 3′. For example, the reverse complement of ATGC is GCAT. This is the operation usually needed when comparing the opposite strand in a sequence editor or considering a reverse primer.

Complement alone changes each base without reversing the order. ATGC becomes TACG, written 3′ to 5′ relative to a 5′ to 3′ input. Reverse alone produces CGTA and changes the reading direction without applying base pairing. The result labels distinguish these operations, because exchanging them can change the interpretation of a primer or sequence match.

Ambiguity letters and RNA

IUPAC ambiguity codes preserve the uncertainty in a base call. R means A or G, and complements to Y, meaning C or T. Likewise, K pairs with M, B with V, and D with H. S, W and N are self-complementary. Reversing a sequence preserves its ambiguity letters; complementing it transforms them according to these pairs.

RNA input is accepted and normalized internally. Choose RNA output to show U instead of T. A mixed T-and-U input is rejected. Paste a plain sequence or one FASTA record; whitespace and position numbers are ignored. The tool processes up to 30,000 bases in your browser.

GC content and next steps

GC percentage uses only definite A, C, G and T bases in its denominator. The result reports how many ambiguous positions were excluded; an entirely ambiguous sequence has no defined percentage here. This is a descriptive sequence calculation, not a melting-temperature estimate.

Download saves the transformed sequence in FASTA format with its orientation in the header. To interpret codons on the other strand, continue with six-frame translation. The codon wheel and amino acid chart provide references for reading the resulting assignments.