= U. Gubler
{c}
\b[<U. Gubler>] is first author, with <B. J. Hoffman>, of a 1983 method for generating <cDNA libraries> from small amounts of <messenger RNA>. The method combined first-strand synthesis with second-strand synthesis mediated by <Ribonuclease H> and <DNA polymerase I>.<A simple and very efficient method for generating cDNA libraries by U. Gubler and B. J. Hoffman>[Gene 25, pp. 263–269, primary byline and Abstract]{ref} This contribution made information in an RNA population accessible through recoverable DNA copies. The published initial is retained without assuming an expanded identity.
A <cDNA library> represents the RNA molecules successfully copied and recovered, rather than automatically representing every gene equally. <Reverse transcription>, second-strand synthesis and subsequent recovery can change representation. A useful library therefore requires more than a high total number of clones: rare transcripts and full-length products must also be considered.
An original sampling calculation isolates the rare-transcript question. Suppose a target transcript has probability $p=0.01$ in each independent recovered clone. The probability that $n$ examined clones contain no target is
$$
P(\mathrm{miss})=(1-p)^n.
$$
For $n=80$, this is about 0.448. Requiring at least 95 percent probability of finding one target gives
$$
n\ge\frac{\log0.05}{\log0.99},
$$
so at least 299 clones are needed under the stated independent-sampling model. Copying bias that lowers the recovered target fraction changes that calculation even if the starting RNA fraction was known.
The primary method paper also tested fidelity against a known transcript sequence.<A simple and very efficient method for generating cDNA libraries by U. Gubler and B. J. Hoffman>[Abstract, full-length sequence validation]{ref} Representation, product length and sequence agreement are distinct measurements. A large library can still undersample a rare transcript or contain truncated copies; neither conclusion follows from clone count alone.
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