Characterization of the 3′ breakpoint of the 118 kb deletion.

<p>(<b>A</b>) Amplification of the 376 bp deletion breakpoint in heterozygous and homozygous individuals with the 118 kb deletion. The normal and mutant alleles are denoted by the 482 bp and 376 bp amplicons, respectively. (<b>B</b>) DNA sequence of the 376 bp breakpoint sequence. The 5′ end of the breakpoint at the δβ-globin intergenic region is un-bolded while its 3′ end is bolded and is at the olfactory receptor cluster breakpoint. The sequences of PCR primers are underlined at both ends. (<b>C</b>) Physical map of the region that separates the two breakpoints shows that it consists of 118,475 bp and encompasses 6 olfactory receptor (OR) genes. (<b>D</b>) Absence of PCR amplification from the β-globin gene and OR genes OR51V1, OR52Z1, OR51A1P, OR52A1, OR52A5, OR52A4 in two individuals homozygous for the 118 kb deletion. PCR analysis of normal (N), heterozygous (Het) and homozygous (Hom) individuals shows the absence of specific amplicons in homozygous individuals only. Amplicons from δ-globin, OR52J1P and OR52E2, which are outside the deleted region are present in all individuals. The top band in each gel represents an internal control (IC) amplicon from the cystic fibrosis gene, which is amplified in the same reaction to demonstrate successful amplification, whenever the target amplicon is deleted.