Allelic Expression of Deleterious Protein-Coding Variants across Human Tissues
(A) The two chromosomal copies (alleles) of a gene are shown in red and blue. In most cases, both alleles are transcribed; this is known as bi-allelic expression (left panel). In the case of allele-specific expression (middle panel), one allele exhibits greater expression than the other allele. When only one allele of a gene is actively transcribed, gene expression is termed monoallelic expression (right panel). (B) RNA-Seq reads across heterozygous sites can discriminate between the two alleles and quantify the relative abundance of expression. Although the relative gene expression levels may be similar, the allelic ratios can vary.