Students can observe and wonder about inheritance by looking around the room at their peers. However, understanding heredity and the link between genotype and phenotype is much more abstract. In just 72 hours, this activity gives students a concrete experience with variation in seedlings' observable traits that are explained by Mendelian inheritance.

Wisconsin Fast Plants® seeds from 4 different stocks—2 homozygous parental stocks and their F₁ and F₂ generations—are germinated in petri dishes where their expression of the dominant purple stem trait is easily identified in just 3 to 4 days. Students then count the numbers of purple and non-purple seedlings. By calculating the ratio of purple stem seedlings to non-purple stem seedlings, students can discover the 3:1 inheritance pattern predicted by Mendelian genetics. Each petri dish grows living data to make Punnett squares come alive!

New Wisconsin Fast Plants® 72-Hour Genetics Kit
Just released! We are proud to offer an easy-to-use kit for teaching students about the inheritance of a trait that is coded for by 1 gene in Wisconsin Fast Plants®. The trait is stem color. The dominant allele causes a purple stem, and the recessive allele causes a non-purple stem. The Wisconsin Fast Plants® 72-Hour Genetics Kit comes with seeds from P₁, P₂, F₁, and F₂ crosses, growing materials, and complete Teacher’s Manual with reproducible Student Guide.

Related Resources

Wisconsin Fast Plants® 72-Hour Genetics Kit Wisconsin Fast Plants® AstroPlants, Seeds

Investigation
Students ask questions about inheritance and conduct an investigation to figure out how the purple stem trait in Wisconsin Fast Plants® is inherited. Students observe and record the stem color of the 2 parental lines and their F₁ and F₂ generation offspring (all grown in petri dishes). These observations are evidence that is very similar to what Gregor Mendel used to explain simple inheritance.

Students can see from analyzing their observations that Wisconsin Fast Plants® seedlings inherit 2 genes for this stem color trait, 1 from each parent. The evidence will also clearly show that there are 2 versions (alleles) of the gene for stem color, and the purple allele is dominant while the non-purple allele is recessive.

Procedure

1. Pose the investigation question: What is the explanation for how parents and offspring can have the same or different traits and how siblings can have the same or different traits?
2. Explain how students will work in small groups to observe and gather evidence about the inheritance of a trait in plants that can be used to answer the investigation question.
3. Assign students to small groups that will place seeds for germination in 4 petri dishes so that each petri dish contains a different line of seeds as listed below:
   
   1. Parent 1
           1) phenotype observed: non-purple stem
           2) genotype will be inferred: homozygous anl/anl
   2. Parent 2
           1) phenotype observed: purple stem
           2) genotype will be inferred: homozygous ANL/ANL
   3. F₁ generation (offspring from intermating Parent 1 lines with Parent 2 lines)
           1) phenotype observed: purple stem
           2) genotype will be inferred: heterozygous ANL/anl
   4. F₂ generation (offspring from intermating F₁ lines)
           1) phenotype observed: a mix of purple stem and non-purple stem that can be analyzed to reveal a ratio of 3
               purple stem to 1 non-purple stem
           2) genotype will be inferred through data analysis to be a 3:1 ratio that provides key evidence for inferring
               the genotypes of the P₁, P₂, F₁, and F₂ lines
   Divide the 100 seeds in each packet of Wisconsin Fast Plants® seed for each line among the number of student groups. Students then place the seeds on white, quilted paper-towel-lined petri dishes that will be kept in a shallow dish of water under 24-hour fluorescent light. In 3 days, the seeds will germinate and seedlings will clearly show the purple-/non-purple-stem traits.
   
   Complete instructions for planting the seeds in petri dishes are included here.
   Note: Which lines are germinated and when they are started can be varied in this activity to change the data students have to work with and the amount of inference required. For example, Parent 2 can be germinated 1 day later so that students must hypothesize about its phenotype and genotype, or the F₂ generation can be delayed until after students develop hypotheses to predict its outcome.
4. Guide students to make careful observations on day 3 and analyze their data. Students can then make inferences about the genotypes based on the 3:1 segregation ratio of the purple stem and non-purple stem phenotypes in the F₂ generation.
5. Assign student groups to propose a hypothesis for how the stem color trait is inherited in Wisconsin Fast Plants®, and explain how the data supports or refutes that hypothesis. A chi-square test can be used by students to analyze data observed that does not fit their hypothesis.

Have student groups listen to and respect the different ideas that other groups present, accept the skepticism of others, and consider alternative explanations that are given.

Learn more
To learn more about our extensive selection of kits for teaching with Wisconsin Fast Plants®, visit www.carolina.com/fastplants, where you can also find secure online shopping, product information, classroom resources, activities, and additional teaching tips.