Sense strand

In genetics, a sense strand or coding strand is the segment of double stranded DNA running from 5' – 3' that is complementary to the antisense strand. The sense strand is the strand of DNA that has the same sequence as the mRNA, which takes the antisense strand as its template during transcription, and eventually undergoes (typically, not always) translation into a protein.

The immediate product of this transcription is a resultant initial RNA transcript, which contains sequencing of nucleotides that are identical to the sense strand. The exception to this is that Uracil is used for nucleotide sequencing of RNA molecules rather than Thymine.

Most Eukaryotic RNA transcripts undergo additional editing prior to being translated for protein synthesis. This process typically involves removal of introns from the initial RNA transcript, the addition of a Methylated Cap at the 5' end, and the addition of a Poly-A Tail at the 3' end. This deletion process is knowns as splicing. The end product is known as a mature mRNA. Prokaryotic mRNA does not undergo the same process.

Strictly speaking, only the mRNA makes "sense" with the genetic code as the translated protein peptide sequence can be directly inferred from this strand. The sense strand DNA however, has a lot of 'garbage' stuffed in between genetic codes. (This is true in most eukaryotic genes. Prokaryotes usually don't have 'garbage' in their sense strand DNA.) The "anti-sense" strand is complementary to the "sense" and is the actual template for mRNA synthesis.

Knowing the difference between the sense and anti-sense strands is important in certain molecular biology applications. For example, in microarray expression technologies, it is important to know which strand is "viewed" on the array. An array can correspond to either strand; however, a single array will be made entirely of "sense" or "anti-sense" strands.

Identifying the different strands is also important in understanding small interfering RNAs, or siRNA.