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Explain

About the Activity:

In this Explain activity, students will investigate the biology behind the aging process. They will examine the importance of genetic variation to human inheritance. They will also compare the genetic aspects of traits with environmental influence and discuss how genetics and environment combine to determine life expectancy.

Objectives:
  • Explain how most human traits involve many genes.
  • Discuss the genetic and environmental components of traits.
  • Examine the genetic and environmental explanations for the aging process.
Materials:

Class Height, Hair Color, and Sex Chromosome Graphs (make transparency)

Genetic Variation Activity

Maximum Animal Life Span Chart (make transparency)

Image from CNN.com

Procedure:
  1. Ask students to name as many human traits as possible. List all replies on the board.

  2. Ask students whether the various traits are genetic or environmental. Make a table that reflects purely genetic traits (cystic fibrosis), purely environmental traits (pierced ears), and traits that are combinations of both (skin color, height, weight).

  3. Explain that aging is a trait also. Humans are 99.9% genetically identical. We all have two legs, two arms, one stomach, etc. And we all age.

  4. Do Genetic Variation Activity.

  5. Organize students into teams of four. Ask teams to create a list of at least ten reasons why they think that humans age.

  6. Ask a person from each team to contribute to a class list. Can their reasons be grouped as genetic and environmental? If so, make these regroupings.

  7. Show students the Maximum Animal Life Span chart. Does this affect their reasoning? Does this indicate a genetic link to life span? If aging is genetic, how many alleles / genes do students think are involved? Could there also be an environmental component?

  8. Pose these questions to begin student thinking:
    1. Genetic theory of aging
      1. Are there one or more genes that ultimately determines life span?
      2. If there is an "aging gene," wouldn't it be possible to have a mutation that would make a person immortal?
      3. Refer to CNN article for background information.
    2. Environmental theory of aging
      1. What if there were cures for every disease (Alzheimer's, cancer, Parkinson's)?
      2. How much longer would these cures extend human life expectancy?
      3. Would we have quality of life if we were free of disease?
      4. What other problems / issues would need to be considered?
  9. Allow students to react to, and discuss, these issues.

  10. Return to the question: "What does it mean to age?" Tell students that in the next lesson, they will investigate various scientific theories on aging.

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