Fig. 1

The target CpG-rich regions within p16 gene body. a The CpG island lying in p16 exon 1 contains 324 nucleotides and 31 CpG sites (grey shading). b The CpG island lying in p16 exon 2 contains 321 nucleotides and 35 CpG sites (grey shading). Using nested PCR with outer primers (the locations were indicated in red type) and inner primers (the locations were indicated by black box), the two target regions were finally amplified, namely one fragment including 313 bp and 31 CpG sites and another including 273 bp and 32 CpG sites