Isolation of the human insulin-like growth factor I gene using a single synthetic DNA probe.

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Abstract
A single synthetic oligonucleotide was employed as hybridization probe to detect and enable isolation of the human insulin‐like growth factor I (IGF‐I) gene from a human genomic DNA library. The synthetic oligonucleotide probe coded for the B‐chain of IGF‐I and was designed for expression in Escherichia coli. Despite numerous interspersed mismatches, the synthetic probe hybridized specifically with seven recombinant lambda phage containing almost the entire B‐chain region of the human IGF‐I gene. The usefulness of this approach was further demonstrated by the detection of lambda phage containing human preproinsulin, using A and B chain synthetic oligonucleotides, 90 and 63 nucleotides in length, as hybridization probes. The nucleotide sequence of the human IGF‐I exon suggests that IGF‐I is synthesized as a larger precursor molecule.