Mutation Causes
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
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Printed: November 7, 2014
AUTHORS
Douglas Wilkin, Ph.D.
Jean Brainard, Ph.D.
www.ck12.org
C HAPTER
Chapter 1. Mutation Causes
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Mutation Causes
• Define mutagen.
• Identify causes of mutation.
• Give examples of spontaneous mutations.
What does radiation contamination do?
It mutates DNA. The Chernobyl disaster was a nuclear accident that occurred on April 26, 1986. It is considered the
worst nuclear power plant accident in history. A Russian publication concludes that 985,000 excess cancers occurred
between 1986 and 2004 as a result of radioactive contamination. The 2011 report of the European Committee on
Radiation Risk calculates a total of 1.4 million excess cancers occurred as a result of this contamination.
Causes of Mutation
Mutations have many possible causes. Some mutations seem to happen spontaneously without any outside influence. They can occur when mistakes are made during DNA replication or transcription. Other mutations are caused
by environmental factors. Anything in the environment that can cause a mutation is known as a mutagen. Examples
of mutagens are pictured in Figure 1.1. For a video about mutagens, go the link below. http://www.youtube.com/w
atch?v=0wrNxCGKCws (0:36)
Spontaneous Mutations
There are five common types of spontaneous mutations. These are described in the Table 1.1.
TABLE 1.1: Common Spontaneous Mutations
Mutation
Description
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TABLE 1.1: (continued)
Mutation
Tautomerism
Depurination
Deamination
Transition
Transversion
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Description
a base is changed by the repositioning of a hydrogen
atom
loss of a purine base (A or G)
spontaneous deamination of 5-methycytosine
a purine to purine (A to G, G to A), or a pyrimidine to
pyrimidine (C to T, T to C) change
a purine becomes a pyrimidine, or vice versa
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Chapter 1. Mutation Causes
FIGURE 1.1
Examples of Mutagens.
Types of mu-
tagens include radiation, chemicals, and
infectious agents. Do you know of other
examples of each type of mutagen shown
here?
The Chernobyl Disaster: Follow-up
Though the area immediately around the Chernobyl disaster may not be safe for human life for thousands of years,
the Exclusion Zone around the Chernobyl nuclear power station has become a haven for wildlife. As humans were
evacuated from the area 25 years ago, existing animal populations multiplied and rare species not seen for centuries
have returned or have been reintroduced, for example lynx, wild boar, wolf, Eurasian brown bear, European bison,
Przewalski’s horse, and eagle owl. Birds nest inside the cracked concrete sarcophagus shielding in the shattered
remains of the nuclear reactor. The Exclusion Zone is so lush with wildlife and greenery that in 2007 the Ukrainian
government designated it a wildlife sanctuary. It is now one of the largest wildlife sanctuaries in Europe.
Summary
• Mutations are caused by environmental factors known as mutagens.
• Types of mutagens include radiation, chemicals, and infectious agents.
• Mutations may be spontaneous in nature.
Making Connections
MEDIA
Click image to the left for use the URL below.
URL: http://www.ck12.org/flx/render/embeddedobject/45570
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www.ck12.org
Explore More
Use this resource to answer the questions that follow.
• What Is Mutation? at http://learn.genetics.utah.edu/content/variation/mutation/ .
1.
2.
3.
4.
5.
When do most mutations develop?
What happens to most of the mutations that develop naturally?
Where in the genome do most mutations occur?
Are most mutations bad? Explain your answer.
What is meant by DNA repair?
Review
1. Define mutation and mutagen.
2. List three examples of mutagens.
3. Distinguish between a transition and a transversion.
References
1. Laura Guerin. Examples of mutagens. CC BY-NC 3.0
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