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Lesson summary for:
Evolutionary processes and patterns inform medicine


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In this activity, students use data and the principles of natural selection to explain the relatively high frequency of alpha-thalassemia in certain populations. They also learn how comparisons of genetic sequences help researchers studying cleft lip and palate, as well as how natural selection has conserved the genetic sequences responsible for these defects.

National Institutes of Health

Grade level:

2 1/2 hours

Teaching tips:
Computer access for learners will increase the efficiency of this lesson, which is particularly relevant for pre-med students.

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

  • Present-day species evolved from earlier species; the relatedness of organisms is the result of common ancestry.

  • Some lineages remain relatively unchanged for long periods of time.

  • Evolution results from natural selection acting upon genetic variation within a population.

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

  • Over time, the proportion of individuals with advantageous characteristics may increase (and the proportion with disadvantageous characteristics may decrease) due to their likelihood of surviving and reproducing.

  • Natural selection can act on the variation in a population in different ways.

  • Natural selection sometimes favors heterozygotes over homozygotes at a locus.

  • Heterozygote advantage preserves genetic variation at that locus (i.e., within the population, it maintains multiple alleles at that locus).

  • Because of common ancestry, model organisms can be used to provide insight into the biology of other organisms.

Teacher background:

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