RACE

=Rapid amplification of cDNA ends=

**Rapid amplification of cDNA ends** (commonly abbreviated to **RACE**; also **one-sided PCR** or **anchored PCR**) is a technique used in transcript analysis to obtain the full sequence of a messenger RNA. The RNA of interest is reverse-transcribed to single-stranded cDNA, which is then amplified in a PCR fashion. The primer used to synthesise cDNA is called a //gene-specific primer//; it hybridises to a known sequence within the mRNA and is extended towards an unknown sequence at either end (either 5' RACE or 3' RACE).

**5' RACE** is useful in identifying the transcription start site on mRNA.

**1**. First, an anti-sense oligonucleotide called the //gene specific primer// is hybridised to a known sequence in the mRNA of interest. **2**. The primer is then extended by reverse transcriptase, using mRNA as a template, to make a single stranded cDNA copy. **3**. //The enzyme terminal deoxynucleotidyl transferase (TdT)// is used to add a string of identical nucleotides to the 3' end of the nascent cDNA, called the //homopolymeric tail//. **4**. The modified cDNA is then used as a template for PCR by annealing a //sense, universal primer// that can anneal to the homopolymeric tail on the 3' end of the cDNA. The cDNA template can be made double-stranded in this way. **5**. Once amplified, the cDNA is cloned into a vector and sequenced. The first base in the sequence that is not a complement of the 3' homopolymeric tail marks the start of the RNA transcript.