Kit mutation analysis in feline neoplastic mast cells. Genomic DNA from feline neoplastic mast cells was extracted, amplified using primers specific for a Kit exon 8 internal tandem duplication (ITD), purified, cloned into plasmids, sequenced, and analyzed by PCR (A) as well as by chromatography (B). (A) Shows ethidium bromide-stained agarose gel electrophoresis results from amplification products from the three feline mastocytoma patients examined (lanes #1, #2, and #3) as well as from a normal cat genomic DNA that served as control (lane #4). The identity of the products was all confirmed by sequencing. A chromatogram of the Kit ITD (obtained in patient #1) compared to wild-type Kit is shown in (B).