The key difference between multiple alleles and lethal alleles is that multiple alleles involve more than just the typical two alleles that usually control a certain character in an organism, while lethal alleles are responsible for the death of the organism that carries them.
An allele is a variant form of a gene. Some genes have a variety of different forms that are located at the same genetic locus on a chromosome. Moreover, humans are called diploid organisms since they have two alleles at each genetic locus, with one allele inherited from each parent of the offspring. Moreover, the genotypic interaction between the two alleles at a locus can be described as dominant or recessive. Based on that, there are three genotypes: homozygous dominant, heterozygous, and homozygous recessive. In addition, due to different effects, various forms of alleles can also be present in organisms. Multiple alleles and lethal alleles are two different forms of alleles.
CONTENTS
1. Overview and Key Difference
2. What are Multiple Alleles
3. What are Lethal Alleles
4. Similarities – Multiple Alleles and Lethal Alleles
5. Multiple Alleles vs Lethal Alleles in Tabular Form
6. Summary – Multiple Alleles vs Lethal Alleles
What are Multiple Alleles?
Multiple alleles are three or more alleles for a particular gene in biology. This phenomenon is known as multiple allelism. A good example of multiple alleles is the ABO blood group system in humans. Typically, in Mendelian inheritance, a given chromosomal locus is occupied by two distinct types of gene alternatives: one dominant allele and one recessive allele. These are the two alleles of the same gene.
Figure 01: Multiple Alleles
However, in some instances, there are more than two alternatives (alleles) existing for a gene. Those instances are referred to as multiple allelism. Therefore, Three or more gene variants that exist for a gene are called multiple alleles. Furthermore, other than ABO blood groups of the humans, coat colour in cats, wings of Drosophila melanogaster (fruit fly), potato tuber in plants, and distinct types of virulence of bacteria are also governed by the multiple alleles.
What are Lethal Alleles?
Lethal alleles are involved in causing the death of the organism that carries them. Lethal alleles are usually a result of mutations in genes that are essential for growth or development. Moreover, these lethal alleles can be recessive, dominant, or conditional, depending on the gene or genes involved. The concept of lethal alleles was first described by Lucien Cuenot in 1905 while he was studying the inheritance of coat colour in mice that is controlled by the agouti gene. It was in 1910 that W.E. Castle and C.C. Little confirmed Cuenot’s work.
Figure 02: Lethal Alleles
Lethal alleles can cause the death of an organism prenatally or at any time after birth. Anyhow, they commonly manifest early in their development. An example of lethal alleles in humans is achondroplasia, a genetic condition that causes dwarfism. The lethal allele is dominant and hence causes the death of the organism when present in a homozygous state (AA). Heterozygotes will possess a short stature or dwarfism, while a homozygous recessive individual will be normal size.
What are the Similarities Between Multiple Alleles and Lethal Alleles?
- Multiple alleles and lethal alleles are two different forms of alleles.
- Both forms of alleles give rise to different phenotypes.
- These alleles follow non-Mendelian inheritance.
- Both forms of alleles are due to mutations.
- They are both present in different organisms other than humans.
What is the Difference Between Multiple Alleles and Lethal Alleles?
Multiple alleles involve more than just the typical two alleles that typically control a certain character in an organism, while lethal alleles are involved in causing the death of the organism that carries them. Thus, this is the key difference between multiple alleles and lethal alleles. A good example of multiple alleles in humans is the ABO blood group system, while a good example of lethal alleles in humans is achondroplasia.
The below infographic presents the differences between multiple alleles and lethal alleles in tabular form for side by side comparison.
Summary – Multiple Alleles vs Lethal Alleles
Alleles are gene alternatives. Multiple alleles and lethal alleles are two different forms of alleles. Multiple alleles involve more than just the typical two alleles that generally control a certain character in an organism, while lethal alleles are responsible for causing the death of the organism that carries them. So, this is the key difference between multiple alleles and lethal alleles.
Reference:
1. “Multiple Alleles – Definition and Examples.” Biology Articles, Tutorials & Dictionary Online, 13 Oct. 2021.
2. “Lethal Allele.” An Overview | ScienceDirect Topics.
Image Courtesy:
1. “Figure 12 02 05” By CNX OpenStax – (CC BY 4.0) via Commons Wikimedia
2. “Lethal alleles punnett square” By Dead_mouse.svg and Mouse.svg: Madprimederivative work: Adabow – This file was derived from:Dead mouse.svg:Mouse.svg: (CC BY-SA 3.0) via Commons Wikimedia