Recombination within the human embryonic xi-globin locus: a common xi-xi chromosome produced by gene conversion of the psi xi gene.
The duplicated human embryonic alpha-like globin genes encode a 5' functional zeta (xi 2) gene and a highly homologous pseudogene (psi xi 1). We have identified chromosomes with a xi 2-xi 1 rather than a xi 2-psi xi 1 arrangement by genomic mapping and oligonucleotide analysis. The DNA sequence of a cloned downstream xi-like gene provides direct evidence for the conversion of a psi xi 1----xi 1 gene, by a xi 2 gene. We present data suggesting that this gene conversion, which removed the only identifiable inactivating mutation in the psi xi 1 gene, was an interchromosomal event. The xi 2-xi 1 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 xi 2 gene are readily detectable.
D000483:Alleles; D000818:Animals; D001483:Base Sequence; D002902:Chromosomes, Human, 16-18; D003001:Cloning, Molecular; D004247:DNA / Q000302:isolation & purification; D004262:DNA Restriction Enzymes; D005260:Female; D005333:Fetus; D005785:Gene Conversion; D005796:Genes; D008040:Genetic Linkage; D005865:Gestational Age; D005914:Globins / Q000235:genetics*; D006801:Humans; D006822:Hybrid Cells / Q000166:cytology; D051379:Mice; D011110:Polymorphism, Genetic; D011247:Pregnancy; D012333:RNA, Messenger / Q000235:genetics; D011995:Recombination, Genetic; D014158:Transcription, Genetic
D012333:RNA, Messenger; D005914:Globins; D004247:DNA; D004262:DNA Restriction Enzymes