Recombination within the human embryonic ζ-globin locus: A common ζ-ζ chromosome produced by gene conversion of the ψζ gene

The duplicated human embryonic α-like globin genes encode a 5′ functional zeta (ζ2) gene and a highly homologous pseudogene (ψζ1). We have identified chromosomes with a ζ2-ζ1 rather than a ζ2-ψζ1 arrangement by genomic mapping and oligonucleotide analysis. The DNA sequence of a cloned downstream ζ-like gene provides direct evidence for the conversion of a ψζ1→ζ1 gene, by a ζ2 gene. We present data suggesting that this gene conversion, which removed the only identifiable inactivating mutation in the ψζ1 gene, was an interchromosomal event. The ζ2-ζ1 arrangement is common in all eight populations studied representing a previously undescribed type of polymorphism between individuals. Stable mRNA transcripts from the converted gene are absent at 16-20 weeks of gestation when transcripts from the ζ2 gene are readily detectable. © 1985.