ABCA7 and Alzheimer disease: Sanger sequencing of a stretch of DNA up to 3 kbp identified a 25 bp repeat within the splice donor site of exon 18 in ABCA7. Subsequent genotyping using Southern blot showed that individuals carrying an allele > 5720 bp (“expanded”), were mostly AD patients [OR 4.5 (95% CI 1.3–24.2), p = 0.008 [46].