Modeling Independent Assortment & Dihybrid Crosses


If your class modeled inheritance using popsicle sticks, this activity builds upon that process.  Here students must examine how two traits are inherited, revealing that each allele has an equal chance of being passed on to the next generation, the principle of independent assortment.     You could also use popsicle sticks to create two sets of chromosomes for your parents, or the worksheet has instructions for students to create their own chromosomes using paper.  A template is included or you can have students make their own.

 Thicker cardstock paper is recommended so that students can’t see what letters (alleles) they are picking up, but you could also do it cheaply with plain white paper and have students color or mark them in some way to keep track of the male and female set.

Students use a Punnett square to show that the inheritance pattern of a dihybrid cross    HhTt x HhTt results in a 9:3:3:1 ration.  When they perform the cross with their paper chromosomes they should find that the ratio is similar, though random chance will likely prevent it from being exactly the same.

AP students could even do this project and apply a chi square analysis on the results, but that is probably beyond its intended audience.

Grade Level:  8-10
Time Required:  35-45 min

HS-LS3-3 Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population.