Main Difference – Mutation vs Polymorphism
Mutation and polymorphism are two terms used to describe DNA variants. DNA variants can occur due to errors in DNA replication or external factors such as UV and chemicals. A mutation refers to a DNA variant in a particular individual whereas polymorphism refers to DNA variants within a population. The main difference between mutation and polymorphism is that mutation is a change in a DNA sequence of the genome of a particular organism whereas polymorphism is a mutation that occurs in more than 1% of a particular population. Mutations can be either hereditary or acquired.
Key Areas Covered
1. What is a Mutation
– Definition, Causes, Types
2. What is Polymorphism
– Definition, Features, Examples
3. What are the Similarities Between Mutation and Polymorphism
– Outline of Common Features
4. What is the Difference Between Mutation and Polymorphism
– Comparison of Key Differences
Key Terms: Acquired Mutations, Chromosomal Mutation, Frameshift Mutations, Hereditary Mutations, Mutation, Polymorphism, Point Mutation, Single Nucleotide Polymorphism (SNP)
What is a Mutation
A permanent alteration of a nucleotide sequence of a gene is referred to as a mutation. Mutations are one reason for observing diversity among individuals within a population. Mutations can occur due to either errors in DNA replication or environmental factors such as UV and chemicals. The size of a mutation can be a single nucleotide change, a change in a few base pairs or a change in a segment of a chromosome. Point mutations are the alterations of a single base pair. Alterations in the segment of a chromosome are called as chromosomal mutations. Point mutations occur due to nucleotide substitutions. These substitutions can cause missense, nonsense or silent mutations in the nucleotide sequence of the gene. Since point mutations bring slight changes into the sequence of a gene, alternative forms of a gene are produced. These alternative forms of a gene are called alleles. Insertions, deletions or duplications of a few base pairs cause frameshift mutations. Gene duplications, translocations, inversions, intra-chromosomal deletions, and the loss of heterozygosity are types of chromosomal mutations.
Figure 1: Mutation due to UV
Mutations can be either hereditary or acquired. Hereditary mutations occur in germline cells. Therefore, they can be inherited by the offspring. But acquired mutations occur in the somatic cells. Therefore, acquired mutations are not often inherited by the offspring.
What is Polymorphism
The presence of more than one allele at a particular locus in a particular population is called polymorphism. If the minor allele frequency of a particular allele in the population is more than 1%, this situation is called as polymorphism. On the other hand, polymorphism can also be considered as a discontinuous genetic variation. During discontinuous genetic variation, several more sharply distinct forms of individuals can be identified within a population. The highest organisms can be divided into two sexes as males and females as a result of discontinuous genetic variation. Blood groups of humans are also an example of discontinuous genetic variation.
Figure 2: Polymorphism in groove snails’ shell
Polymorphism persists over generations by generations since it is not affected by the natural selection. That means polymorphism brings neither advantages nor disadvantages upon individuals. Biochemical techniques are required in order to discriminate between some of the polymorphisms since they do not bring any visible manifestations. The mode of nutrition of social insects is an example of this type of polymorphisms.
Similarities Between Mutation and Polymorphism
- Both mutation and polymorphism are DNA variants.
- All mutations and polymorphisms do not bring visible manifestations.
Difference Between Mutation and Polymorphism
Definition
Mutation: A permanent alteration of a nucleotide sequence of a gene is referred to as a mutation.
Polymorphism: The presence of more than one allele at a particular locus in a particular population is referred to as polymorphism.
Significance
Mutation: A mutation is a physical event.
Polymorphism: Polymorphism is a population attribute.
Single Base Pair Changes
Mutation: A single base pair change in the nucleotide sequence of a gene is called a point mutation.
Polymorphism: A single base pair change in the nucleotide sequence is called a single nucleotide polymorphism (SNP).
Examples
Mutation: Sickle cell anemia, hemophilia, cystic fibrosis, Klinefelter syndrome, and Turner syndrome occur due to mutations.
Polymorphism: ABO blood group and the gender of humans are the examples of polymorphism.
Effect of Natural Selection
Mutation: Natural selection selects the mutations that are best suited for the environment.
Polymorphism: Natural selection does not affect alleles that brings polymorphism.
Conclusion
Mutation and polymorphism are two types of DNA variants. Mutation is an alteration of the nucleotide sequence of a gene. If a mutation occurs in a population with a frequency of more than 1%, the mutation is called a polymorphism. A mutation refers to a DNA variant in a particular individual whereas polymorphism refers to DNA variants within a population.The main difference between mutation and polymorphism is the frequency of occurrence of each type of variants within the population.
Reference:
1. “What is a gene mutation and how do mutations occur? – Genetics Home Reference.” U.S. National Library of Medicine. National Institutes of Health, n.d. Web. Available here. 03 Aug. 2017.
2. “What kinds of gene mutations are possible? – Genetics Home Reference.” U.S. National Library of Medicine. National Institutes of Health, n.d. Web. Available here. 03 Aug. 2017.
3. “Polymorphism.” Encyclopædia Britannica. Encyclopædia Britannica, inc., n.d. Web. Available here. 03 Aug. 2017.
Image Courtesy:
1. “DNA UV mutation” By NASA/David Herring – NASA, [1] (Public Domain) via Commons Wikimedia
2. “Polymorphism in Cepaea nemoralis” By Chiswick Chap – Own work (CC BY-SA 3.0) via Commons Wikimedia
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