Learning Objective

In this lesson we will learn about genetic mutations and the different ways they can be classified.

Learning Outcomes

By the end of this lesson you will be able to:

  • Explain what a mutation is and compare the different types, including:
  • Chromosomal mutations and DNA mutations
  • Spontaneous mutations and induced mutations.
  • Somatic mutations and gametic mutations.
  • Harmful, beneficial and neutral mutations.
  • Identify different types of chromosomal mutations: deletions, duplications, inversions, insertions and translocations.
  • Identify different types of DNA mutations: substitutions, insertions and deletions.

 

 genetic mutation worksheet  year 10 biology pdf workbook

Click images to preview the worksheet for this lesson and the Year 10 Biology Workbook.

 

Genetic Mutations

  • A genetic mutation is an alteration of the genetic composition of a cell or organism.
  • Mutations can be classified in several ways:
  • How much genetic material is involved – chromosomal mutations and DNA mutations.
  • How they originate – spontaneous mutations and induced mutations.
  • Where they originate – somatic mutations and gametic mutations.
  • Their effect on an organism – harmful, beneficial and neutral mutations.

 
drosophila genetic mutation wings

Some of the first studies on genetic mutation were conducted using fruit flies.

(Image: Thomas Morgan Hunt, Wikimedia Commons)

 

Chromosomal Mutations and DNA Mutations

  • Chromosomal mutations and DNA mutations differ by how much genetic material is involved.

 

Chromosomal Mutations

  • Chromosomal mutations involve sections of chromosomes or whole chromosomes.
  • Examples of chromosomal mutations include:
  • Deletion – the removal of a section of a chromosome.
  • Duplication – the copying of a section of a chromosome.
  • Inversion – the reversal of the orientation of a section of a chromosome.
  • Insertion – the transfer of a section of a chromosome between non-homologous chromosomes.
  • Translocation – the exchange of sections of chromosomes between non-homologous chromosomes.

 
chromosomal mutation deletion duplication inversion

Mutations involving single chromosomes include deletion, duplication and inversion.

(Image: YassineMrabet, Wikimedia Commons)

 
 
chromosomal mutations insertion translocation

Mutations involving non-homologous chromosomes include insertion and translocation.

(Image: YassineMrabet, Wikimedia Commons)

 

DNA Mutations

  • DNA mutations involve individual genes or sites between genes.
  • Examples of DNA mutations include:
  • Substitution – a single nucleotide is replaced by another nucleotide.
  • Insertionone or more nucleotides are added to a DNA molecule.
  • Deletionone or more nucleotides are removed from a DNA molecule.

 
dna point mutation substitution

Substitution involves the replacement of one nucleotide with another.

 
 
dna frameshift mutation insertion

Insertion involves the addition of one or more nucleotides.

 
 
dna frameshift mutation deletion

Deletion involves the removal of one or more nucleotides.

 

Spontaneous Mutations and Induced Mutations

  • Spontaneous mutations and induced mutations differ by how they originate in cells.

 

Spontaneous Mutations

  • A spontaneous mutation is caused by factors within a cell.
  • An example of a spontaneous mutation is an error during DNA replication that results in the wrong nucleotide being added to a newly synthesised strand of DNA.

 
spontaneous mutation dna replication error

Spontaneous mutations arise due to errors in cell processes such as DNA replication.

 

Induced Mutations

  • An induced mutation is caused by environmental factors, known as as mutagens, which can cause diseases such as cancer.
  • Examples of mutagens include:
  • Radiation – ionising radiation, which includes X-rays, gamma rays and UV radiation.
  • Chemical mutagens – includes many chemical compounds, such as nicotine, benzene and mustard gas.
  • Biological mutagens – some viruses, such as human papillomavirus (HPV) and hepatitis B, and bacteria, such as Helicobacter pylori, can cause cancer.

 

 induced mutation ionising radiation  induced mutation chemical mutagen  induced mutation virus

Mutagens are environmental agents that can induce mutations.
They include ionising radiation, chemical mutagens and some viruses and bacteria.

 

Somatic Mutations and Gametic Mutations

  • Somatic mutations and gametic mutations differ by the type of cell they occur in and whether they can be inherited or not.

 

Somatic Mutations

  • Somatic mutations originate in somatic cells (body cells).
  • They are acquired during an organism’s lifetime and cannot be passed on to future generations.

 
somatic mutation skin cancer

Somatic mutations, such as skin cancer, cannot be passed on to future generations.

(Image: Kelly Nelson, Wikimedia Commons)

 

Gametic Mutations

  • Gametic mutations (germline mutations) originate in gametes (sex cells).
  • Once these mutations are acquired, they can be passed on to future generations, where they will occur in both somatic cells and gametic cells.

 
gametic germline mutation albinism

Gametic mutations, such as albinism, can be passed on to future generations.

(Image: Apdency, Wikimedia Commons)

 

Harmful, Beneficial and Neutral Mutations

  • Harmful, beneficial and neutral mutations differ by their effect on the fitness (health) and survivability of individuals.

 

Harmful Mutations

  • Harmful mutations (deleterious mutations) are mutations that decrease the fitness and survivability of individuals.
  • Harmful mutations change the end-product of a gene to a less efficient or non-functional form.
  • The effect can range from being only slightly negative to being lethal.
  • Examples of harmful mutations include genetic diseases, such as cystic fibrosis and haemophilia.

 
harmful deleterious mutation polka dot zebra

Deleterious mutations reduce the fitness and survivability of individuals.

(Image: Lori Ellis, Adobe Stock)

 

Beneficial Mutations

  • Beneficial mutations (advantageous mutations) are mutations that increase the fitness and survivability of individuals.
  • Beneficial mutations change the end-product of a gene to a more efficient form or create a new function altogether.
  • Examples of beneficial mutations are those that make individuals stronger, or more resistant to a particular disease, or more tolerant to a particular environmental stress, such as drought.

 
beneficial advantageous mutation thorny devil

Advantageous mutations increase the fitness and survivability of individuals.

(Image: Christopher Watson, Wikimedia Commons)

 

Neutral Mutations

  • Neutral mutations are mutations that have no effect on the fitness and survivability of individuals.
  • Neutral mutations include:
  • Mutations in non-coding regions of DNA.
  • Mutations that occur in a gene but do not affect the product of that gene.
  • Mutations that result in a new phenotype that has neither a positive nor negative effect on an individual in their current environment.
  • An example of this type of neutral mutation is blond hair.

 
neutral mutation heterochromia

Neutral mutations have no effect on the fitness and survivability of individuals.

(Image: Public Domain Pictures)

 

Summary

  • A genetic mutation is an alteration of the genetic composition of a cell or individual.
  • Chromosomal mutations involve sections of chromosomes or whole chromosomes. They include:
  • Deletions – the removal of a section of a chromosome.
  • Duplications – the copying of a section of a chromosome.
  • Inversions – the reversal of the orientation of a section of a chromosome.
  • Insertions – the transfer of a section of a chromosome.
  • Translocations – the exchange of sections of chromosomes.
  • DNA mutations involve individual genes or sites between genes. They include:
  • Substitutions – the replacement of a single nucleotide by another.
  • Insertions – the addition of one or more nucleotides.
  • Deletions – the removal of one or more nucleotides.
  • Spontaneous mutations are caused by errors within a cell.
  • Induced mutations are caused by mutagens, including radiation, chemicals and biological agents.
  • Somatic mutations originate in body cells.
  • They cannot be passed on to future generations.
  • Gametic mutations (germline mutations) originate in sex cells.
  • They can be passed on to future generations.
  • Harmful mutations (deleterious mutations) decrease the fitness and survivability of individuals.
  • Beneficial mutations (advantageous mutations) increase the fitness and survivability of individuals.
  • Neutral mutations have no effect on the fitness and survivability of individuals.

 
genetic mutation two-headed snake

(Image: Eric Isselée, Adobe Stock)

(Header Image: nobeastsofierce, Adobe Stock)

 

 genetic mutation worksheet  year 10 biology pdf workbook

Click images to preview the worksheet for this lesson and the Year 10 Biology Workbook.