Figure 2: Identification of homozygous CFTR mutation in the patient with CBAVD and NOA. (a) Pedigree of family with inherited CFTR mutation. Unfilled squares and circles denote unaffected male and female family members, respectively. Filled squares denote affected males; half black and white symbols denote heterozygous members; black arrows indicate proband. (b) The CFTR mutation was verified by Sanger sequencing. Homozygous CFTR mutation in the proband (II:3) was inherited from heterozygous parental carriers (I:1 and I:2). Rectangle indicates position of mutation. (c) The CFTR p.G970D mutation at exon 18 causes G-to-A substitution at cDNA (NCBI reference sequence: NM_000492.4) nucleotide position 2909, replacing glycine (G) with aspartic acid (D) at amino acid 970 in the CFTR protein. Arrowheads indicate the mutation site. (d) Sequence alignment shows conservation of affected amino acid (glycine) across various species. The asterisks are defined for amino acid number interval. WT: wild-type; MT: mutation; CFTR: cystic fibrosis transmembrane conductance regulator; TMD: transmembrane domains; NBD: nucleotide binding domains; cDNA: complementary DNA; NCBI: National Center for Biotechnology Information; R domain: disordered area - regulatory area; CBAVD: congenital bilateral absence of vas deferens; NOA: nonobstructive azoospermia.