Quantification of exogenous and endogenous KRAS transcript levels in the small intestine of mutant mice. KRAS transcript levels were measured using quantitative PCR analysis. RNA was extracted from paraffin-embedded intestinal tissue samples. Endogenous (mouse) and exogenous (human) KRAS expression was measured and compared against β-actin. Fold changes were calculated for KRAS levels against β-actin levels using the 2-ΔΔCt method of relative quantification . (A) Relative fold changes in exogenous (human) KRAS transcript levels in mutant mice compared to the wild type (WT) mice (designated as 1). (B) Relative fold changes in mouse Kras and human KRAS transcript levels in different regions (D = duodenum; J = jejunum; I = ileum) of the mutant mouse intestines.