Contents
What is an allelic imbalance?
Allelic imbalance (AI) is a phenomenon where the two alleles of a given gene are expressed at different levels in a given cell, either because of epigenetic inactivation of one of the two alleles, or because of genetic variation in regulatory regions.
What is allelic expression?
When only one allele of a gene is actively transcribed, gene expression is termed monoallelic. Gene expression is termed “monoallelic” when only one of the two copies of a gene is active, while the other is silent.
What is allelic data?
Allelic expression (AE; also called allele-specific expression or allelic imbalance) analysis is becoming an increasingly important tool for this, as it quantifies expression variation between the two haplotypes of a diploid individual distinguished by heterozygous sites (Fig. 1a).
What is allele-specific analysis?
Allele-specific expression (ASE) analysis, which quantifies the relative expression of two alleles in a diploid individual, is a powerful tool for identifying cis-regulated gene expression variations that underlie phenotypic differences among individuals.
What causes loss of heterozygosity?
Loss of heterozygosity (LOH) is defined as the loss of one parent’s contribution to the cell, can be caused by direct deletion, deletion due to unbalanced rearrangements, gene conversion, mitotic recombination, or loss of a chromosome (monsomy).
What is allele balance?
The proportion of reads covering a variant’s location that support the variant. For example, if a variant’s location is covered by 100 reads, of which 25 support the variant and 75 do not, then the variant would have an allelic balance of 25/100 = 0.25.
Can two alleles be expressed?
In most cases, both alleles are transcribed; this is known as bi-allelic expression (left). However, a minority of genes show monoallelic expression (right). In these cases, only one allele of a gene is expressed (right).
What is it called when both alleles are expressed in offspring?
​Codominance Codominance is a relationship between two versions of a gene. Individuals receive one version of a gene, called an allele, from each parent. In codominance, however, neither allele is recessive and the phenotypes of both alleles are expressed.
What is an allelic mutation?
Allelic heterogeneity is the phenomenon in which different mutations at the same locus lead to the same or very similar phenotypes. These allelic variations can arise as a result of natural selection processes, as a result of exogenous mutagens, genetic drift, or genetic migration.
What is meant by an allele?
An allele is a variant form of a gene. Some genes have a variety of different forms, which are located at the same position, or genetic locus, on a chromosome. Humans are called diploid organisms because they have two alleles at each genetic locus, with one allele inherited from each parent.
How is LOH detected?
Loss of heterozygosity (LOH) results from a deletion of small or large chromosomal regions and often correlates with the loss of important tumor suppressor genes located in these areas. LOH is typically detected by FISH or by PCR amplification of microsatellite loci followed by capillary gel electrophoresis.