page_title: Paired-end tag
section_title: Constructing the PET library
hierarchical_section_title: Paired-end tag / Constructing the PET library
caption_attribution_description: English: PET library construction workflow
context_page_description: Paired-end tags are the short sequences at the 5’ and 3’ ends of a DNA fragment which are unique enough that they exist together only once in a genome, therefore making the sequence of the DNA in between them available upon search or upon further sequencing. Paired-end tags exist in PET libraries with the intervening DNA absent, that is, a PET "represents" a larger fragment of genomic or cDNA by consisting of a short 5' linker sequence, a short 5' sequence tag, a short 3' sequence tag, and a short 3' linker sequence. It was shown conceptually that 13 base pairs are sufficient to map tags uniquely. However, longer sequences are more practical for mapping reads uniquely. The endonucleases used to produce PETs give longer tags but sequences of 50–100 base pairs would be optimal for both mapping and cost efficiency. After extracting the PETs from many DNA fragments, they are linked together for efficient sequencing. On average, 20–30 tags could be sequenced with the Sanger method, which has a longer read length. Since the tag sequences are short, individual PETs are well suited for next-generation sequencing that has short read lengths and higher throughput.
context_section_description: PET libraries are typically prepared in two general methods: cloning based and cloning-free based.
caption: Workflow of Cloning and Cloning-free based PET library construction.
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