High PAPR signal is difficult to amplify without sacrificing its power conversion efficiency at the linear power amplifier (PA).
For example, expanded CAG/CTG repeats are notoriously difficult to amplify and this can sometimes lead a falsely negative outcome in which the expanded allele is not detected.
It is difficult to amplify fragments of DNA more than 300 base pairs from old samples [4], [6].
Although the YY1 promoter had more than 90% GC content and was initially difficult to amplify, we successfully cloned it into a luciferase reporter (Figure S3a).
However, the standard fragment is difficult to amplify and often generates NUMT sequences in fig wasps, so further exploration of markers is desirable.
Non-seed plants (bryophytes, lycophytes and monilophytes) were generally the most difficult to amplify, particularly cox1 (where attempted), matK and psbK psbI.
Of the remaining 14 genes, 6 proved difficult to amplify or clone, but 8 were successfully engineered as C-terminal fusions with a yellow fluorescent protein (YFP) reporter.
They can be more difficult to amplify because of their low copy number, and because online databases often contain fewer comparable sequences from which amplification primers can be designed.
It is important to stress that the COI fragment amplified here is shorter than the full standard barcoding fragment, but the latter is difficult to amplify and often generate pseudogene sequences in fig wasps.
The universal primers used for amplification of V9 recognize practically all eukaryotic phyla, even those that are well known to be particularly difficult to amplify, like Amoebozoa or Foraminifera [3].
In addition, in recent S-WGA studies, insufficient chromosome amplifications in the S-WGA products were found in both PCR- and MDA-based WGA using array CGH techniques [25], [32], [33], suggesting that some chromosomes are difficult to amplify by the S-WGA experiments.
