Difference Between Allelic and Locus Heterogeneity

The key difference between allelic and locus heterogeneity is that allelic heterogeneity is the ability of different mutations within the same gene to cause the same disease while locus heterogeneity is the ability of mutations in a number of different genes to cause the same disease.

Genetic heterogeneity is the ability of different genetic mechanisms to produce the same or similar phenotypes. Mutations in different loci of the same gene or mutations in different genes can produce genetic heterogeneity. There are two types of genetic heterogeneity as allelic and locus heterogeneity. Allelic heterogeneity describes the ability of different mutations within the same gene (different alleles at a locus) to produce variable expression of a condition, especially a disease. Locus heterogeneity describes the ability of mutations at different gene loci to cause the same disease phenotype.

CONTENTS

1. Overview and Key Difference
2. What is Allelic Heterogeneity
3. What is Locus Heterogeneity
4. Similarities Between Allelic and Locus Heterogeneity
5. Side by Side Comparison – Allelic vs Locus Heterogeneity in Tabular Form
6. Summary

What is Allelic Heterogeneity?

Allelic heterogeneity is the ability of different mutations within the same gene to cause the same disease. In other words, allelic heterogeneity is the production of a similar phenotype by different alleles within the same gene. This indicates the possibility of multiple different mutations in the same gene. Many of the mutations are single nucleotide alterations or changes. Allelic heterogeneity can arise due to several reasons, including natural selection, exogenous mutagens, genetic drift, or genetic migration.

Cystic fibrosis is the best example of a disease caused by allelic heterogeneity. Different mutations (approximately 1500 mutations) within the gene CFTR can cause cystic fibrosis. Another example is Alkaptonuria, which is a rare genetic disease in humans.

What is Locus Heterogeneity?

Locus heterogeneity is a type of genetic heterogeneity which produces a similar phenotype by mutations at different loci/genes. In other words, locus heterogeneity is the ability to produce a similar phenotype or identical phenotypes through mutations in a number of different genes, especially two or more genes.

Cornelia de Lange syndrome is the best example of a disease caused by locus heterogeneity. This disease can be acquired through a single mutation in any of five different genes: NIPBL, SMC1A, HDAC8, RAD21, and SMC3. In contrast to allelic heterogeneity, locus heterogeneity is “nonallelic”.

What are the Similarities Between Allelic and Locus Heterogeneity?

• Allelic and locus heterogeneity are two types of genetic heterogeneity.
• They produce the same phenotype or identical phenotypes via different genetic mechanisms.
• They occur as a result of mutations in gene locus or loci.

What is the Difference Between Allelic and Locus Heterogeneity?

In allelic heterogeneity, different alleles in the same gene can cause a similar phenotype while in locus heterogeneity, mutations in different genes or loci can cause a similar phenotype. So, this is the key difference between allelic and locus heterogeneity. Cystic fibrosis is an example of a disease caused by allelic heterogeneity while Cornelia de Lange syndrome is an example of a disease caused by locus heterogeneity.

Below infographic of the difference between allelic and locus heterogeneity shows more comparisons between both.

Summary – Allelic vs Locus Heterogeneity

Allelic and locus heterogeneity are two types of genetic heterogeneity which produce similar or identical phenotypes via genetic mechanisms, especially mutations. Allelic heterogeneity refers to the production of the same phenotype via different mutations occurring in the same gene. In contrast, locus heterogeneity refers to the production of identical phenotypes via mutations occurring in the different genes or loci. Thus, this is the key difference between allelic and locus heterogeneity. Different alleles at a locus are responsible for allelic heterogeneity while different loci or genes are responsible for locus heterogeneity.

Reference:

1. Keith, Benjamin & Robertson, David & Hentges, Kathryn. (2014). Locus heterogeneity disease genes encode proteins with high interconnectivity in the human protein interaction network. Frontiers in genetics. 5. 434. 10.3389/fgene.2014.00434.