Females heterozygous for the recessive second chromosome mutations px, sp, and cn are mated to a male homozygous for all three mutations.The offspring are as follows:
$\begin{array}{|l|r|}\hline p x  s p  c n & 1461 \\\hline p x  s p  c n^{+} & 3497 \\\hline p x  s p{+ c n} & 1\\\hline p x  s p^{+}  c n+ & 11 \\\hline p x^{+}  s p  c n & 9 \\\hline p x^{+}  s p  c n+ & 0 \\\hline p x^{+}  s p+ c n & 3483 \\\hline p x^{+}  s p+ c n+ & 1539 \\\hline & 10,000 \\\hline\end{array}$
-Which of the three genes is in the middle?

Question

Females heterozygous for the recessive second chromosome mutations px, sp, and cn are mated to a male homozygous for all three mutations.The offspring are as follows:

\begin{array}{|l|r|}\hline p x &nbsp;s p &nbsp;c n & 1461 \\\hline p x &nbsp;s p&nbsp; c n^{+} & 3497 \\\hline p x&nbsp; s p{+&nbsp;c n} & 1\\\hline p x&nbsp; s p^{+}&nbsp; c n+ & 11 \\\hline p x^{+} &nbsp;s p &nbsp;c n & 9 \\\hline p x^{+} &nbsp;s p &nbsp;c n+ & 0 \\\hline p x^{+}&nbsp; s p+&nbsp;c n & 3483 \\\hline p x^{+}&nbsp; s p+&nbsp;c n+ & 1539 \\\hline & 10,000 \\\hline\end{array}

-Which of the three genes is in the middle?