Missense mutation of the last nucleotide of exon 1 (G->C) of beta globin gene not only leads to undetectable mutant peptide and transcript but also interferes with the expression of wild allele.

Hemoglobin Monroe (beta globin G->C, codon 30) is a missense mutation. We could not detect either the mutant peptide or transcript in reticulocyte-enriched preparation and in expanded erythroid progenitor cells. By quantitative gene expression assay beta globin mRNA was found to be reduced by more than 70% in all heterozygous subjects with different haplotypes. We conclude that this mutation also interferes with expression of wild type allele.