Question

In Next Generation Illumina sequencing, what are the two purposes for the DNA tails added to the ends of the processed sample fragments?

a) Provide a fluorescent signal to be captured by the imaging software
b) Enable reverse transcription to take place when extracting RNA
c) Ensure the library fragments are no longer than a few hundred base pairs
d) Provide a binding site for the primers involved in the synthesis reaction
e) Bind to flow cell oligos, capturing the sample libraries

Answer 1

In Next Generation Illumina sequencing, DNA tails are added to the ends of the processed sample fragments to provide a binding site for the primers involved in the synthesis reaction and to bind to flow cell oligos, capturing the sample libraries.

Step-by-step explanation:

The DNA sample to be sequenced is denatured (separated into two strands by heating it to high temperatures). The DNA is divided into four tubes in which a primer, DNA polymerase, and all four nucleoside triphosphates (A, T, G, and C) are added. In addition, limited quantities of one of the four dideoxynucleoside triphosphates (ddCTP, ddATP, ddGTP, and ddTTP) are added to each tube respectively. The tubes are labeled as A, T, G, and C according to the ddNTP added. For detection purposes, each of the four dideoxynucleotides carries a different fluorescent label. Chain elongation continues until a fluorescent dideoxy nucleotide is incorporated, after which no further elongation takes place. After the reaction is over, electrophoresis is performed. Even a difference in length of a single base can be detected. The sequence is read from a laser scanner that detects the fluorescent marker of each fragment. For his work on DNA sequencing, Sanger received a Nobel Prize in Chemistry in 1980.