Genetic mutation

 Introduction to Genetic Mutation

Mutation is a healthy or unhealthy alteration in the genetic makeup of an individual. Genetic mutation can lead to a structural or numerical manipulation of the DNA sequence that aids in the variation of species ”. The mutation is essential for the gradual transformation of traits from one generation to another in an evolutionary way. However, some times a mutation can cause aberration of the genes that lead to permanent genetic disorders. Most often, the mutation occurs when different alleles are inherited from the egg and the sperm

 

Causes and risk factors of mutation 

Mutations may occur naturally or may be induced by environmental factors. Some of the factors causing mutation are the prolonged exposure of individuals to radiation, medication, or viral infections. Being pregnant too early (before 18 years) and too late( after 40 years) favour mutation because chromosomal nondisjunction during the cell division is increasingly common in these age groups. On the other hand, the age of the father ( sperm)  directly affects the quality and number of sperms resulting in failure of fertilization or mutation. This is evident in men aged more than 40 years as the aged sperms tend to form a wrong nucleotide sequence. Furthermore, environmental factors like pollution, exposure to chronic ultraviolet radiation and chemical irritants can increase the risk of mutation. Above all, the genetic errors inherited from the parental genes play a key role in the mutation.

 

Forms of mutation

There are 2 major forms of mutation; germinal mutation and somatic mutation. If the genetic abnormalities are formed during the process of fertilization, they are known as the germinal mutations. If the mutations occur during fetal or embryonic development but not at the time of fertilization then they are termed as somatic mutations. In many cases, children are asymptomatic until they enter their school age. There are many forms of mutation but the most common ones are discussed here. Firstly,  Non-disjunction is the failure of chromosome pairs to separate during the cell cycle. Non -disjunction results in the derangement of the physical structure of chromosomes. If the mutation affects the arrangement of the chromosome`s arms, it is called translocation. Inversion results in the nucleotide sequence being arranged in a reverse mannerA bit rare form of mutation is the deletion where a  part of the chromosome is deleted. Deletion can easily hamper the order of gene arrangement thereby causing mutation. Mutation can affect the victims both genotypically and phenotypically, sometimes they take a serious form where gene therapy may not work.

 

Nonsense mutation  

 

 

 

Missense mutation

 

 

Insertion Defect

 

 

Frameshift Mutation

 

 

Duplication Error

 

 

Deletion Error

Mutation types-Images by US National Library of Medicine

 

 

Consequences of mutation- a genetic approach

  1.  Mutations interfere with protein synthesis by altering the nucleotides responsible for the formation of amino acids.

  2. Changes in the nucleotide sequence can lead to chronic conditions such as sickle cell disease, haemophilia, and some congenital illnesses of the heart.

  3. In some cases, gene mutations can cause stillbirth (baby is born dead).

  4. Kids suffered from mutation tend to manifest lower levels of intelligence, poor physical, emotional and social development.

  5.  One of the common causes of congenital cancer is a mutation. Many cell studies have proved the correlation between cancer and genes.

 

Benefits of mutation

Most of the mutations are harmful, however, very few healthy genetic alterations benefit the species. Mutations produce a new version of proteins that will enable the organisms to adapt to drastic changes within the environment. In other words, they increase the organism’s chances of survival and reproduction. It is believed that thick fur on the animal skin, especially in the polar region, is a consequence of natural mutation over the long period. Another example is bacteria that can survive in the presence of antibiotic drugs is as a result of the mutant gene. 

 

 

Read more

1.      

Introduction to genetics and heredity

2.

Gene mutation

3.

Human genome project

4.

Disorders and defects of chromosomes    

5.

Mendelian inheritance

 

Questions

  1. Define mutation. Explain the difference between germinal mutation and the somatic mutation.

  2. What are the causes of mutation?

  3. How can mutation benefit the species?

  4. Explain the most common forms of mutation.

 

 



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