Pass It Down
This lesson uses two consecutive hands-on genetics to calculate the frequency of different traits in a class. First, frequency of our class’s facial traits, such as ear lobe attachment, is calculated. Second, the ability to taste various chemicals, such as PTC, is tested. Students make predictions throughout the lesson and discuss whether the traits are dominant or recessive based on the outcomes. The lesson could be completed with just the first segment if taste papers are not easily acquired. Students handouts and a powerpoint are provided. The extension of this activity is to create a pedigree based on a family and their PTC tasting traits. Students must understand the relationship between genes, chromosomes, genotypes, and phenotypes. Students must also understand how a pedigree works and be able to infer whether a trait is dominant or recessive based on pedigree information. This directly relates to the u201cchecku201d of applying data to complete and interpret a genetic pedigree.
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- Students will calculate the frequency of facial traits (phenotypic probabilities) found within their class
- Students will form an evidence based opinion about the genetics of taste and decide whether taste is determined by nature or nurture.
Activity 1: Frequency of Facial Traits
- Create a class video of various facial traits examined in this activity. The video can be shown to introduce the activity to future classes, generate student excitement, and initiate parental involvement.
Activity 2: Genetics of Taste
- Students can create a family pedigree about the ability to taste PTC. However, many students in class would be unable to complete a personal family pedigree. Some students may be adopted and would have no biological link to other family members. Some students may have step parents and step siblings, which can often complicate completing a pedigree. Some students may not have a family large enough to complete a pedigree with conclusive information. BE SENSITIVE TO THESE ISSUES IN CLASS, and proceed with caution in how this extension activity is handled. I have found it best to let one student volunteer to test their family members for the ability to taste PTC (assuming they are genetically related to all members tested and have a fairly large family – the more members the better!) and allow the entire class to use that data to create a family pedigree. Send home a “control envelope” and an “experimental envelope” with the appropriate amount of taste strips in each. An example of results that could be obtained and a completed pedigree is included in the Teacher Handout: Genetics of Taste!!! See attachments. Remember, the ability to taste PTC (or Thiourea) is a dominant trait!
Materials for Activity: Frequency of Facial Traits
- Teacher’s Guide: Frequency of Traits
- Student Handout: Frequency of Facial Traits
- wipe-off board or projector to display data table
Materials for Activity: Genetics of Taste
- Teacher’s Guide: Genetics of Taste
- Student Handout: Genetics of Taste
- Control taste strips*
- PTC taste strips*
- Thiourea taste strips*