Southern analysis of the DAZ genes on the Y chromosomes of great apes. (A) Genomic structures of the human DAZL and DAZ genes. Exons 2–6 encode the RNA recognition motif and exon 7 encodes the DAZ repeat. Three DAZ genes encoding one, two, and three RRMs, respectively, are shown. NsiI sites are indicated with vertical arrows, and the sizes of NsiI fragments detected by probe A are given at left. (B) Southern analysis of Region A – the RRM blot. Genomic DNA samples from humans (Hsa), bonobos (Ppa), chimpanzees (Ptr), gorillas (Ggo), and orangutans (Ppy) were digested with NsiI and blotted with probe A. The autosomal DAZL fragments are indicated with A's at left. (C) Southern analysis of Region B – the DAZ repeat blot. The blots were hybridized with probe B that detects all exon 7 repeating units. (D) Determination of the DAZ gene copy number – the DAZ dosage blot. The probe contained a mixture of the human DAZ and DAZL 3'UTRs. The human male sample contains 4 DAZ genes. The relative intensities of the DAZ and DAZL signals and the derived DAZ gene copy numbers are listed underneath the blots. Due to reduced similarity with the human probe and the high copy number, the copy numbers of orangutan DAZ gene could not be determined accurately. (E) Quantification of the hybridization signals of the DAZ dosage blots in (D). The DAZ peaks are at the left. (F) Determination of the DAZ gene copy number in rhesus macaque. The left four lanes contain E. coli DNA samples spiked with known amounts of rhesus macaque DAZ and DAZL 3'UTRs. (See Methods for details.) The probe contains a mixture of rhesus macaque DAZ and DAZL 3'UTRs. This figure only shows representative samples with different hybridization patterns. The results of all samples are described in Supplementary Table S1 (see Additional file 1).