In their study, the researchers referred to the common allele as «T,» and
the less common allele, which produces less BDNF protein, as «C.»
Of the nearly 50,000 modified cxcr4
alleles analyzed across five independent experiments, 81.1 % (range 75.3 — 81.7 %) contained pure deletions from 1 — 64 bp in size with the most
common deletions being 2, 9, 12, 15, 18, and 25 bp, while 13.5 % (range 12.8 — 16.9 %) of cxcr4
alleles contained pure insertions ranging from 1 to 69 bp with more than 90 % being 7 bp or
less (Figure 1B).
To identify
common functional variants, the authors used an allelic transmission disequilibrium test (TDT), which determines if an
allele is transmitted more (or
less) than we'd expect by chance.