= Solution
Summing the transmission table by its rows and columns gives
$$
\begin{array}{c|cc}
&\text{transmitted}&\text{not transmitted}\\\hline
\text{allele 2}&59&49\\
\text{allele 1}&41&51
\end{array}
$$
Thus the marginal case-versus-pseudo-control <odds ratio> is
$$
\boxed{\widehat{\mathrm{OR}}=\frac{59/41}{49/51}=\frac{3009}{2009}\simeq1.498.}
$$
This is the requested approximate allelic effect. Keeping the parent-specific matching instead gives the discordant-pair <odds ratio> $c/b=30/20=1.5$, numerically close here. Neither calculation makes the within-family <allele> observations independent population samples.
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