RAD51 and head and neck cancer: As all RAD51 paralogs are generally considered conservative with the frequency of missense mutations being very low, we recently focused on single nucleotide polymorphisms (SNPs) occurring in promoter, 5′ untranslated region (5′UTR) of exon 1 and intron 1 of these genes and found that genetic variability of XRCC3 and RAD51 may be of relevance with respect to head and neck cancer (HNC) [29].