Q:
Does the PCR reaction volume (negatively) influence the outcome?
A: No,
especially since the introduction of the small, thin walled, 0.2
ml plastic vials fitting the 96 well metal blocks of the thermocyclers.
A number
of observations are worth mentioning:
- if using
older model thermocyclers (without a heated lid), to
run small volume PCR reactions, mineral oil is necessary to
cover the reaction mixture. Use of oil increases the volume
of liquid in the vial and thus can influence somewhat the outcome.
Besides, older thermocyclers require the use of larger plastic
vials, with thicker walls, that fit less well in the metal blocks
and thus may increase the likelihood of variation in PCr outcome.
- small,
thin-walled plastic vials designed for the 96 well
metal blocks are ideal for running small-volume PCR reactions.
Due to the heated lid of the thermocyclers, there are no mineral
oil requirements. When tested, reactions yielded similar results,
whether the reaction volume was 100, 25 or 5 microliters.
- It is
important to mention, that small volume PCRs may be very beneficial
when using small amounts of DNA template. In general,
at a constant amount of template DNA, the yield of PCR product
per microliter reaction is higher when the reaction volume is
5 µL compared to 100 µL. This may allow visualisation
of the PCR products, sometimes invisible when larger reaction
volumes are used.
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