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Science on the Road

Classroom Days

Life Science: Who Are You?


Pre-visit Activity:

Effect of Sample Size
Study the occurrence of a hereditary trait with simple pattern of dominant and recessive genetic inheritance in a large population.

Students poll at least 100 students in the school (depending on the size of your school, you may decide to poll just your grade, or several classes, or even the whole school). Questions you can ask: A. Are you right or left handed? Or B. Can you roll your tongue?

Figure the percentage of the population which displays each trait. The theoretical percentages would be 75% right handed, 25% left handed; and 75% capable of rolling tongue, 25% incapable.

We will use this in the discussion when we talk about the benefits of using a larger sample when looking at probability of inheriting a trait.

Probability
Inheriting genes from your parents involves chance. Students should have some idea of what probability means. For example, there is a fifty-fifty chance of having a girl each time you have a baby. Just because a family already has 5 boys doesn't mean that the next baby has to be a girl ö the chance is still 50-50.

Provide each student with a penny. Have them toss it 10 times and graph the results. How many students have exactly half heads and half tails? Now cumulatively take the results they got and graph them together as a class. Are the results closer to 50-50? Discuss that having a larger population sample is necessary for probability and statistics to be valid.

Post-visit Activity:


  1. Extend the "Unique You" activities done in the Classroom Discovery Day to families. Have students take sheets home and see if any family members display the recessive traits.
  2. Ask one of the lefties in the class to find out which extended family members are left-handed and which are right-handed. With this information, construct a family pedigree.
  3. Construct DNA models to show the basic "4 letter" code of genetics. Use the website directions at ology.amnh.org to make 3-D models of DNA in the twisted ladder or double helix pattern.
  4. The students will learn how to extract long strands of DNA from wheat germ. Use the website directions at gslc.genetics.utah.edu to yield large quantities of DNA that can easily be collected.


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