Mutation – Class 12 | Chapter – 9 | Biology Short Notes Series PDF

Mutation: Mutation is a change in the DNA sequence of a cell’s genome, which can be caused by various factors such as errors during DNA replication, exposure to environmental agents (e.g. radiation, chemicals), or viral infections. Mutations can occur naturally or artificially. They can result in alterations in the traits or functions of the affected organism and can be beneficial, neutral or harmful. Mutations play a central role in evolution, providing the genetic diversity that allows species to adapt to changing environments. They can also be the underlying cause of genetic disorders and cancers.

Types of Mutations

• Point mutations: A single nucleotide is substituted, deleted, or inserted in the DNA sequence.

• Frameshift mutations: Addition or deletion of nucleotides that changes the reading frame and affects all codons downstream.
• Chromosomal mutations: Changes in the number or structure of chromosomes, such as duplications, deletions, inversions, or translocations.
• Missense mutations: A point mutation that changes a single nucleotide and results in a different amino acid in the protein product.
• Nonsense mutations: A point mutation that creates a premature stop codon in the protein product, leading to a truncated and often non-functional protein.
• Silent mutations: A point mutation that does not result in a change to the amino acid in the protein product.

• Regulatory mutations: Alterations in the non-coding regions of DNA that affects gene expression.

Causes of Mutation

• Spontaneous mutations: These occur randomly and are due to errors in DNA replication or problems with DNA repair mechanisms.

• Environmental factors: Exposure to radiation, chemicals, or viruses can cause mutations.
• Inheritance: Mutations can be passed down from parent to offspring through genetic inheritance.
• DNA damage: Physical or chemical damage to DNA can cause mutations.
• Mutagenic agents: Certain agents, such as certain chemicals and viruses, can cause mutations by directly altering the DNA sequence.

• Errors during meiosis: Mistakes during cell division can result in changes in the number or arrangement of chromosomes.

Effects of Mutation

The effects of mutations can be diverse and can vary depending on the specific mutation and the organism it occurs in. Some of the potential effects of mutations include:

• Alteration of traits or functions: Mutations can result in changes to the appearance, behavior, or biological functions of an organism.
• Genetic disorders: Mutations can cause genetic disorders such as sickle cell anemia, cystic fibrosis, and Huntington’s disease.
• Cancer: Mutations in certain genes can contribute to the development of cancer by enabling cells to grow and divide in an uncontrolled manner.
• Evolution: Mutations can provide the genetic diversity that allows species to adapt to changing environments, which can drive evolutionary change.
• Loss of function: Some mutations can result in the loss of function of a gene or its protein product, potentially leading to decreased fitness or death of the affected organism.

• Gain of function: Other mutations can result in the gain of new or improved functions, which can contribute to the survival and reproduction of the affected organism.

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By Team Learning Mantras