Mathematics and Society - OS X Lion Server

ANALYZINGTRAITSThe following are some physical traits that can be observed. The first exampleillustrates some of the activities that can be done. Similar types of activitiescould be done with the remainder of the traits.Are you a taster or a nontaster? A harmless chemical called PTC* (phenylthiocarbimide)can be used to test this trait. A small strip of paper soaked in PTC canbe given to each student. Tasters will probably experience a bitter tast~whilenontasters will experience nothing. (It might be wise to have some candy availableto counteract the bitter taste. Let the nontasters have some, also.) Have studentstabulate the results and find the percent of the class that are tasters. About 70%of Caucasians are taster~ while about 90% of Blacks are tasters.Tasting is dominant (a Tt combination will be a taster) over nontasting, so thethree possible genotypes would be TT, Tt and tt, while the phenotypes would be tasters(TT or Tt) and nontasters (tt). Grids could be drawn to show some possibilities.Percents, ratios or fractions could be emphasized.T T T t TTTTTTTTTtHTtTttTtH100% tastersNV\I\50% genotype TT50% genotype Tt3:1 ratio oftasters tonontastersNV\I\1:2:1 ratio ofgenotypes TT,Tt, tt1 2 tasters1"2 nontastersNV\I\1"2 genotype Tt1"2 genotype tt*Add 650 mg of phenylthiocarbamide to 1 litre of water.Boil to dissolve thechemical. Allow the solution to cool. The chemical or prepared PTC strips can bepurchased from most suppliers of biological or chemical materials.The following is a tree diagram of several families.possible genotypes TT, Tt or tt.ADAPTED FROM:Children and Ancestors in Action Biology Series by Stanley L. Weinbergand Herbert J. Stoltz, Copyright © 1974 by Allyn and Bacon, Inc.Used by permission of Allyn and Bacon, Inc.Genetic Continuity, and Why You're You, Intermediate Science Curriculum Study.Permission to use granted by D. C. Heath and Company, and Silver Burdett GeneralLearning Corporation.For each, mark in the165