Mutations

Key Concepts

• Mutagen
• Mutant
• Mutation
• Evolution
• Genetic disorders

Introduction:   

We have observed organisms Mutations undergo changes in their characters due to environmental factors, availability of food, chemicals, pollution etc.  

These organisms change over time due to some environmental factors and the changes happen internally in their genes as well, which are carried to the next generation. 

A change in the genetic material is called mutation. This means changes in the DNA sequence or the chromosomes which carry the DNA. 

Explanation: 

• Mutations can result from various factors like they can occur without any influence of external factors within the cell by DNA copying mistakes made during cell division, or by external factors by exposure to ionizing radiation, exposure to chemicals called mutagens, or infection by viruses. 
• Anything that causes mutation is known as mutagen. For example: UV radiation and Benzoyl peroxide are mutagens. 
• A mutant is the one that undergoes the mutation. For example, Darwin’s finches. 

Factors causing mutations 

A mutation that arises in body cells that are not passed to the next generations is called somatic mutation.  

A mutation or a change that occurs in a gamete or in reproductive cells, which are carried to the next generation without affecting the adult are known as germ-line mutations. 

Germ line and somatic mutation 

Mutations can have diverse effects. They are mainly harmful. Others have little or no effect and sometimes, even though very rarely, the change in DNA sequence may still turn out to be useful to the organism and give rise to evolution, e.g., Darwin’s finches. 

Mutations are categorized into three types depending on the effect they create on the organism.  

1. Beneficial Mutations: 

Certain mutations have a positive influence on the organism in which they occur, these mutations generally happen to adapt to the new environmental situations and lead to evolution. These are known as beneficial mutations.  

They become common through natural selection. 

They increase an organism’s chances of survival or reproduction, and slowly become very common over a period. 

2. Harmful Mutations: 

A genetic disorder is defined as a disease caused by a mutation in one or a few genes and that can be inherited to the next generation. An example in human beings is cystic fibrosis.  

A mutation that gets a negative change in DNA which can produce adverse effects is called harmful mutation. 

Genetic disorders or cancers are outcomes of harmful mutations. 

Cystic fibrosis 

The corn kernels having different color reduce the productivity of corn.  

Different colors of corn kernels 

3. Neutral Mutations: 

The majority of mutations are neither harmful nor beneficial to the organism in which they occur. These mutations are known as neutral mutations.  

There is no positive or negative effect on the organism due to the change in DNA. 

Summary:

• A mutation is a change in the genetic material. This means changes to the DNA or to the chromosomes which carry the DNA.
• A mutation that occurs in body cells that are not passed to subsequent generations is a somatic mutation.
• A mutation that occurs in a gamete or in a cell that gives rise to gametes are special because they carry the same to the offspring or next generation and may not affect the adult at all. Such changes are called germ-line mutations.
• Mutations can result from DNA copying mistakes made during cell division, exposure to ionizing radiation, exposure to chemicals called mutagens, or infection by viruses.
• Depending upon the effects the mutations create on organisms, mutations are categorized into three types

1. Beneficial mutations 2. Harmful mutations 3. Neutral mutation

• Mutations that have a positive effect on the organism in which they occur. They are called beneficial mutations.

• Harmful mutation is a change in DNA which can affect an organism negatively.
• Most mutations have neither negative nor positive effects on the organism in which they occur. These mutations are called neutral mutations.
• Mutations are essential for evolution to occur because they increase genetic variation and the potential for individuals to differ.
  Most mutations are neutral in their effects on the organisms in which they occur.
• Beneficial mutations may become more common through natural selection.
• Harmful mutations may cause genetic disorders or cancer.