Ct distribution of 13 candidate reference genes.

<p>Values are given as the cycle threshold (Ct). Expression levels of the different genes tested are shown as the 25^th and 75^th quartiles (upper and lower hinges), median (central horizontal lines) and whiskers. Whiskers represent maximum and minimum Ct values. Genes are shown from the most (lower Ct, <i>left</i>) to the least abundantly expressed (higher Ct, <i>right</i>).