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The Meaning of Genetic Variation


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Students investigate variation in the beta globin gene by identifying base changes that do and do not alter function, and by using several internet-based resources to consider the significance in different environments of the base change associated with sickle cell disease.

National Institutes of Health

Grade level:

two 50 minute periods

Teaching tips:
This activity is the second in a series entitled Human Genetic Variation. We also recommend the introductory activity in this module: Alike but Not the Same. Before beginning this activity, students should understand basic Mendelian patterns of inheritance, especially autosomal-recessive inheritance; the basic structure of DNA; the transcription of DNA to messenger RNA; and the translation of messenger RNA to protein. This activity largely focuses on variation but could easily be extended or modified to emphasize variation's role in evolution to a greater degree.

Correspondence to the Next Generation Science Standards is indicated in parentheses after each relevant concept. See our conceptual framework for details.

  • Evolution results from selection acting upon genetic variation within a population. (LS4.B)

  • Mutations are random.

  • Traits that confer an advantage may persist in the population and are called adaptations. (LS4.B, LS4.C)

  • Inherited characteristics affect the likelihood of an organism's survival and reproduction. (LS4.B, LS4.C)

  • Depending on environmental conditions, inherited characteristics may be advantageous, neutral, or detrimental.

  • Natural selection acts on phenotype as an expression of genotype.

  • There is variation within a population. (LS3.B)

Teacher background:

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