Molecular biology / sequence processing · BEGINNER LESSON
Reverse complement
A reverse complement is a DNA sequence made by first reversing the original order and then replacing each base with its complementary base. In practice, this is used to compare a sequence with the opposite strand of DNA.
What it is
A reverse complement is a transformed nucleic-acid sequence, usually DNA. DNA stands for deoxyribonucleic acid, and its bases are A, T, C, and G. In a reverse complement, the sequence is read backward and each base is replaced by its pairing base: A with T, and C with G. NCBI, the National Center for Biotechnology Information, uses this operation when it says to reverse complement an input sequence so it matches the reverse complementary strand of a coding sequence.
[1] Sequence Processing at NCBI [2] Regions Enriched with Reverse Complement Triplets in Bacterial ...
How it works
The process has two steps. First, reverse the sequence so the last base becomes first. Second, replace every base with its complement. For example, a strand containing a coding region may need this transformation to represent the opposite DNA strand. The sources also show that reverse-complement transformation can be applied to longer regions when studying sequence symmetry, and that some sequences can be compared this way for pattern search.
[1] Sequence Processing at NCBI [2] Regions Enriched with Reverse Complement Triplets in Bacterial ...
Why it matters
Reverse complements are useful because DNA is double-stranded, so one strand can be described by the other. They are also used in pattern analysis. One source describes searching for regions enriched in reverse complement triplets, where the sequence is rotated 180 degrees and complemented. Another source shows that sequences complementary to a ribosome binding site can pair with it in RNA, reducing translation and RNA levels. RBS means ribosome binding site, the place where ribosomes attach to start translation; RNA means ribonucleic acid; and CDS means coding sequence.
[2] Regions Enriched with Reverse Complement Triplets in Bacterial ... [1] Sequence Processing at NCBI
Limitations and cautions
Reverse complement is a sequence operation, not a statement that two sequences are identical in biology. It only changes order and base pairing. Also, a sequence can be reverse complemented for different reasons: database checking, symmetry analysis, or studying pairing with other regions. The sources do not say that every reverse complement has the same biological effect; some effects depend on where the sequence is located and whether it can base-pair with another region.
[1] Sequence Processing at NCBI [2] Regions Enriched with Reverse Complement Triplets in Bacterial ...
SEE THE IDEA
Reverse complement transformation
A sequence written in one direction.
Read the bases from end to start.
Swap A↔T and C↔G.
The transformed sequence used for comparison or analysis.
The sequence is reversed first, then each base is replaced by its complement.
A reverse complement is built by changing direction and base pairing, not by adding new information.
TRY IT YOURSELF
Test your understanding
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PUT IT TOGETHER
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4 pairs to match
Sources and further reading
This general lesson was generated from public source material. It explains a concept; it does not interpret a private paper or provide medical advice.