Mutation: Definition, Theory, Causes and Effects

What Is Mutation 

According to mutation definition, mutations are variations in the DNA sequence that are a major source of biological variety. These changes take place at several levels and can have significantly disparate implications. In biological systems that may reproduce, we must first determine if they are inherited; specifically, certain mutations impact only the person that carries them, whereas others impact all of the host organism’s children and descendants.

Definition of mutation explains that mutations must arise in cells that create the next generation and modify the hereditary material to impact an organism’s progeny. Finally, the interaction of environmental stresses and hereditary mutations results in species diversification.

Mutation Definition in Biology

Mutations arise when a DNA gene is disrupted or altered so that the genetic information carried by that gene is altered. 

A mutagen is a chemical agent that can lead to a permanent change in the physical makeup of a DNA gene, altering the genetic information.

Although there are many other molecular alterations, “mutation” usually refers to the variation that alters the nucleic acids. These nucleic acids are the building blocks of DNA in biological organisms and are the building blocks of either DNA or RNA in viruses. 

One way to conceive of DNA and RNA is as chemicals that store the information needed for an organism’s replication in the long run. This section concentrates on DNA mutations, although consider that RNA is susceptible to roughly the same mutation factors.

What Are Somatic Mutations?

According to the mutation definition, when mutations happen in non-germline cells, they are referred to as somatic mutations. Somatic mutations are derived from the Greek term soma, which means “body,” and they only impact the current organism’s body. Somatic mutations are unimportant from an evolutionary standpoint unless they occur routinely and modify some essential attribute of a person, such as survival capacity. 

Cancer, for example, is a powerful somatic mutation that affects the survival of a single organism. On the other hand, evolutionary theory primarily concerns DNA alterations in the cells that form the next generation.

Hugo De Vries Theory: Evolutionary Mutation Theory

Hugo de Vries (1848—1935) was a Dutch botanist and one of Mendelism’s independent rediscoveries who presented his thoughts on the genesis of new species in 1901. He also addressed some of Darwin’s theory’s criticisms.

According to him, new species are generated by the abrupt development of changes, which he refers to as mutations. Hugo de Vries claimed that mutations are inherited and passed down through generations. 

Experiments Conducted

Hugo de Vries studied Oenothera Lamarckian (Evening Primrose) and discovered various abnormal forms. When O. Lamarckian was self-pollinated and its seeds were allowed to mature, most F1 plants resembled the parents, but a few were distinct.

The various plants were also self-pollinated, and when their seeds were spread, the bulk of the plants was identical to the parents. However, a few were still with a variety of plants, and this pattern persisted for many generations. Hugo de Vries suggested from his tests that new hereditary features may develop abruptly without any previous evidence of their presence in the race.

What Is Saltation? 

Hugo de Vries felt that evolution is caused by mutation rather than the tiny heritable variations indicated by Darwin. Darwin’s variations are modest and directed, whereas mutations are unpredictable and directionless. Darwin felt that evolution is progressive. However, Hugo de Vries believed that mutation causes species development, known as single-step mutation or saltation.

Key Features of Mutation Theory

Hugo de Vries (1901) proposed a mutation theory of evolution based on the above data. According to the hypothesis, evolution is a jerky process in which new types and species are generated through mutations (discontinuous variations), which serve as raw material for evolution. The following are the most notable characteristics of mutation theory:

• Evolution’s basic material is mutations or discontinuous variations.
• Mutations emerge unexpectedly. They are instantly functioning.
• Unlike Darwin’s continuous changes or fluctuations, mutations are not centred on the species’ mean or typical character.
• The same sort of mutation might develop in several individuals of the same species.
• All mutations can be passed from parent to child.
• Mutations occur in every imaginable direction.
• Nature selects beneficial mutations. Lethal mutations are removed. However, less dangerous and ineffective ones can survive in the offspring.
• The accumulation of variations results in the emergence of new species. A lone mutation can sometimes lead to the creation of contemporary species.

Points in the Mutation Theory’s Favour:

• Mutations are the source of all variants, hence the fountain head of evolution.
• The notion of mutation can explain both advanced and retrograde evolution.
• Because the mutation ratio differs across individuals and their components, mutation theory may explain the emergence of both modified and unchanging forms.
• Several mutations have occurred in the past. Mutations are also generated. They have spawned new kinds.
  • Ancon Sheep is a short-legged breed that arose unexpectedly in Massachusetts in 1791.
  • In 1889, hornless cattle emerged as a mutation from homebred cattle.
  • A single mutation can result in a new variety and even plant species, such as Cicer Gigas, Red Sunflower, Delicious Apple, Noval Orange, etc.
  • Mutations have resulted in hairless and double-toed cats.

Points against the Mutation Theory (Mutation Theory Criticism):

• Hugo de Vries’ Oenothera Lamarckian was a complicated heterozygous form with chromosomal abnormalities, not a normal plant.
• Natural mutations are not as numerous as Hugo de Vries believed.
• The majority of the mutations are unfavourable or regressive.
• Mutations are frequently recessive, but features that participate in evolution are usually dominant.
• Mutation theory fails to explain the evolution of the mutual reliance on pollinating insects and flowers.

Significance of Theory

Hugo de Vries’ Theory of Mutation is significant in understanding the meaning of mutation since it focuses on mutations directly. However, it was eventually shown that evolution could not proceed only through mutations. Natural selection and mutant isolation were also necessary for evolution.

Types of DNA Mutations

Mutation class	Mutation type	Description	Resultant human disease
Point mutation	Insertion	A frameshift occurs when one or more additional nucleotides are introduced into replicating DNA.	One form of beta-thalassemia
	Deletion	One or more nucleotides are “skipped” or otherwise, are removed during replication, leading to a frameshift.	Cystic fibrosis
	Substitution	During replication, one base is erroneously inserted and substitutes the pair at the equivalent position on the complementary strand.	Sickle-cell anaemia
Chromosomal mutation	Deletion	A chromosomal region is deleted, leading to the lack of all the genes for that region.	Cri du chat syndrome
	Duplication	When a chromosomal region is repeated, the dosage of the genes in that area increases.	Few cancers
	Inversion	One chromosomal segment is flipped and reinserted.	Opitz-Kaveggia syndrome
	Translocation	A portion of one chromosome is abnormally linked to another.	One form of leukemia
Copy number variation	Expanding trinucleotide repeat	The standard number of repeating trinucleotide sequences is increased.	Fragile X syndrome, Huntington’s disease
	Genetic amplification	A locus’s number of tandem copies is raised.	Few forms of breast cancers

Causes of Mutation 

Definition of mutation explains that mutation causes genetic differences across animals. Positive mutations are passed down across generations.

For example, sickle cell anaemia is the result of a mutation in the haemoglobin gene. The RBCs form a sickle shape. However, in the African population, this mutation gives malaria protection. Cancer is caused by a mutation in the gene that controls cell division.

The following factors induce the mutation:

Internal Factors

The meaning of mutation explains that the majority of mutations develop when the DNA fails to duplicate correctly. All of these mutations result in evolution. During cell division, DNA duplicates itself. The DNA duplicate is not always flawless, and this little deviation from the original DNA is referred to as a mutation.

External Factors

When DNA is subjected to certain chemicals or types of radiation, it begins to degrade. The UV rays disrupt the thymine dimers, resulting in altered DNA.

Effects of Mutation

A genetic change can have a big effect, but in many situations, evolutionary change results from the accumulation of numerous minor changes. Depending on the context or place, mutational impacts might be helpful, detrimental, or neutral. The majority of non-neutral mutations are harmful. In general, the greater the number of base pairs impacted by a mutation, the greater the influence of the mutation and the greater the likelihood of the mutation being detrimental.

Researchers have begun to quantify distributions of mutational consequences (DMEs) to estimate how many mutations happen with what effect a particular attribute of a biological system to truly comprehend the impact of mutations. The attribute of interest in evolutionary research is fitness, but in molecular genetics, other developing traits may also be of interest. It is extremely difficult to collect meaningful information regarding DMEs because the accompanying effects range from fatal to neutral to favourable; also, various confounding variables frequently hamper these assessments.

To complicate matters further, many mutations interact with one another to change their effects; this is known as Epistasis. Despite this uncertainty, modern research has consistently shown that vast genetic mutations have few consequences. Extensive research is needed to learn more about DMEs and the meaning of mutation.

Summary

According to the definition of mutation, mutation rates can differ both within and across genomes. Researchers will need to do a lot more work before getting more exact estimates of the prevalence of certain mutations. The emergence of high-throughput genome sequencing tools raises the prospect of a more thorough and exact knowledge of mutation rates. Because mutation is a crucial factor in evolution, such research is expected to be critical.