Primer

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In molecular biology, an oligonucleotide is referred to as a primer (Pl .: the primer; IPA : [ ˊp bezeichnetaɪ̯mɐ ]) , which serves as the starting point for DNA replicating enzymes such as DNA polymerase .

DNA polymerases require a hydroxy group as a starting point for their first linkage reaction . With their 3'-OH end, primers provide a suitable hydroxyl function. Primers can consist of both DNA and RNA . During replication , RNA is used as primer material in prokaryotes and eukaryotes . In prokaryotes, the primase , also known as DnaG protein, synthesizes the primer sequences. In eukaryotes, the DNA polymerase α has a primate function. DNA synthesis on the telomeres of eukaryotic cells is a special case . Here, the polymerizing enzyme telomerase uses the 3'-OH end of the DNA as a primer sequence. In prokaryotes, the emerging during replication primers are 5'-3 ' exonuclease activity of the polymerase I or by the RNase H removed. In eukaryotic cells, the primers are removed by displacing DNA synthesis of the polymerase δ and restriction by the flap endonuclease . Allele-specific oligonucleotides bind to certain SNPs .

Also, in the in vitro - amplification of DNA, for example in the polymerase chain reaction (PCR) , the DNA sequencing or the reverse transcription , primers are required. The specific DNA segment to be amplified can be determined here with the aid of the primer.

Primer design

The targeted design of primers is called primer design. For the PCR method, nucleotide sequences that flank the DNA segment to be amplified are determined. According to these sequences, suitable primer sequences are now produced by phosphoramidite synthesis . A primer represents the opposite strand to its “primer partner”. Primers for PCR approaches are usually 18–30 nucleotides in length. Various biotechnology companies now offer tailor-made primers for molecular biology applications. Customized mismatch primers can also be used to introduce specific mutations into genes using the PCR technique . B. exist in the exchange of an amino acid.

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