Serendipitous cloning of a mitochondrial cDNA and its polymorphism

A cDNA clone p5x23 was isolated from a library prepared from membrane bound mRNA from a human lymphoblastoid cell line. This clone was shown to detect a restriction fragment length polymorphism with the enzyme MspI, with frequency for the minor variant of about 10% in a Caucasian population. The clone apparently only detected homozygotes, and did not hybridize to any of a panel of human-mouse somatic cell hybrids containing all human chromosomes in various combinations. Sequence analysis of the clone showed that it encoded a part of the 3' end of the human mitochondrial cytochrome b gene.