Is a random primer or oligo(dT) better for RT-PCR reaction?

Which NGS library preparation kit can be used after generation of cDNA with TeloPrime?
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Is a random primer or oligo(dT) better for ..

Any primer used for Second Strand cDNA Synthesis has to be designed with a partial Illumina P5 adapter extension. Adapter sequences are kept short pre-PCR in order to allow for efficient removal of short fragments during the purification step (steps 14 and 18 ).The full Illumina P5 (Read 1) adapter sequence will only be introduced during PCR (step 29).
Partial Illumina P5 Adapter Sequence (Read 1) for Second Strand Synthesis Primer:
5’ CACGACGCTCTTCCGATCT – NNNNNN(NN) – Target sequence (mRNA-sequence) 3’

and random primers, meaning that a new cDNA synthesis reaction ..
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cDNA synthesis using random hexamer vs. oligo dt …

Three types of primers can be used for RT reaction: oligo (dT) primers, random (hexamer) primers and gene specific primers with each having its pros and cons.

cDNA synthesis using random hexamer vs
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The concentration of a target-specific RT primer should be around 12.5 nM – 1.25 µM final concentration (in this case it would mean you would need 5 µl of a 50 nM – 5 µM target-specific primer). The total concentration of oligos in the First Strand Synthesis reaction should not exceed 2 µM. The higher the primer concentration the higher the likelihood of unspecific binding. However, the exact primer concentration and reaction temperature (up to 50 °C for first strand synthesis and second strand synthesis) strongly depends on the custom primer(s) used and has to be optimized accordingly.

RNA/Reverse Transcription (RT) & cDNA Synthesis …
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Oligo(dT)15 Primer - Promega Corporation

Obviously, a major factor to consider is the choice of reverse transcriptase used to synthesize cDNA. Since each of the available enzymes has different enzymatic properties, one may be more suitable for a specific experiment than the others. Among the enzyme properties to consider are:

Simplify Your First-Strand cDNA Synthesis

Any primer used for First Strand cDNA Synthesis has to be designed with a partial Illumina P7 adapter extension. Adapter sequences are kept short pre-PCR in order to allow for efficient removal of short fragments during the purification step (steps 14 and 18 ). The full Illumina P7 (Read 2) adapter sequence will only be introduced during PCR (step 29 ).
Partial Illumina P7 Adapter Sequence (Read 2) for First Strand Synthesis Primer:
5’ GTTCAGACGTGTGCTCTTCCGATCT- Target sequence 3’
Here the target sequence has to be the reverse complement to the mRNA-sequence in question. The chosen target sequence should be as specific as possible with a Tm that is as close as possible to the intended reaction temperature. In most cases 20 nts are enough. Target sequences should not exceed a length of 50 nts. The entire primer including the Illumina Adapter sequence should not excced 75 nts. The optimal primer length is 45 – 50 nts (Illumina Sequence plus targeted sequence).

Concentration; Oligo(dT) 15 Primer

The NucleoTrap mRNA kit provides latex beads covalently modified with oligo(dT), which allow for isolation and purification of mRNA from total RNA or directly from cells or tissue.

full-length cDNA synthesis is initiated by oligodT primed ..

NucleoTrap mRNA kits contain spin filters, as well as all the necessary reagents and buffers for isolating highly pure poly(A) mRNA from total RNA preparations. The purified mRNA is ready for use in downstream applications, such as cDNA library construction, blotting techniques, RT-PCR, in vitro translation, expression arrays, and differential display. mRNA enrichment is especially recommended for construction of cDNA libraries and demanding blotting procedures, since it reduces background signals.