SMARCA4 and cancer: Since some focal deletions in cancer can occur within small genomic areas and may result in the deletion of parts of genes rather than large chromosomal segments, we next conducted qPCR at three different points along the BRG1 gene (BRG1 exons 3, 18, and 36) to evaluate any deletions involving the front, end or middle of the BRG1 gene, which spans 100 kb on chromosome 19p13.2 [35].