<i>Kras</i>-4A is expressed at higher levels in susceptible (A/J) than resistant (C57BL/6) strains.

<p>Expression levels of <i>Kras</i>-4A (a) and <i>Kras</i>-4B (b) isoforms were measured by qPCR in normal lung of 11 A/J and 11 C57BL/6 mice. * <i>P</i> = 7.1×10⁻⁵, ANOVA. The line within each box represents the median of square root transformed values; upper and lower edges of each box are 75^th and 25^th percentiles, respectively; upper and lower bars indicate the highest and lowest values less than one interquartile range from the extremes of the box.