Mutations: When DNA Is Copied Wrong

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  • 0:02 What Are Mutations?
  • 1:48 Types of Mutations
  • 3:19 Causes of Mutations
  • 4:24 Lesson Summary
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Lesson Transcript
Instructor: Jayne Yenko

Jayne has taught health/nutrition and education at the college level and has a master's degree in education.

In this lesson, we will learn how mutations, or errors in DNA, come about, what kinds of effects they may have, and how they can impact populations as a whole.

What Are Mutations?

Have you ever wondered why you have brown hair and blue eyes, and your sibling has blond hair and brown eyes? It has to do with DNA - our genetic code that comes from our parents. Sometimes mistakes are made in the DNA when it is replicated or copied as each cell divides. When that happens, it can affect our appearance, how we behave, even whether we live or die.

An organism's DNA affects how it looks and behaves, and its physiology. A change in the DNA can cause changes in all aspects of its life. We often think of mutations as something negative, but that isn't always the case.

These errors, or changes in DNA, are essential to evolution. Without them, evolution could not occur. Usually, mutations are not good or bad, they're just different.

Mutations create slightly different versions of the same genetic information. The different versions are called alleles. They are what make each of us unique, by creating variation in hair color, skin color, height, shape, behavior, and our ability to fight off disease.

Variations that help an organism survive and reproduce are passed on to the next generation. Variations that hinder an organism's ability to survive and reproduce cause the organism to be eliminated from the population - in other words, the organism dies. This process, called natural selection, can lead to important changes in appearance, behavior, and/or physiology, in just a few generations. So, what are some of the types of mutations that occur?

Types of Mutations

There are many types of DNA errors. The effects they may have on the individual vary from none at all to death. Mutations can be grouped into categories that are based on where the mutations occur.

  • Somatic mutations, or acquired mutations, take place in non-reproductive cells. These are usually not passed on to the offspring. These can alter the division of cells, however. First example, the 'stop' codon may be altered, which would cause cells to divide out of control, resulting in cancer.
  • Germ-line mutations occur in reproductive cells. These kind of mutations are passed on to the offspring. An example is albinism.

Mutations can also be categorized by the length of the nucleotide sequences they affect.

  • Gene-level mutations are changes to short lengths of nucleotides. These affect physical characteristics and are important to large-scale evolution. An example would be insects becoming resistant to the insecticide DDT after repeatedly being exposed to it.
  • Chromosomal mutations are changes to long lengths of nucleotides. These have serious consequences. An example is Down syndrome, where there are three copies of chromosome 21 instead of just two. This significantly affects the individual's appearance, cognition, and behavior.

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