Wisconsin Fast Plants® Monohybrid Crosses Inquiry

A Carolina Essentials™ Investigation

Total Time: 1 hour

Prep: 30 mins | Activity: 1 hour

Life Science


High School


In this scientific inquiry activity, students germinate F2 generation Wisconsin Fast Plants® seeds and identify the phenotypes and possible genotypes of the F2 generation plants. Based on phenotypic ratios, the genotype may be refined. Monohybrid crosses are performed using Punnett squares to test possible genotypes for the parental and F1 generations of plants. Students design an investigation based on Mendelian monohybrid crosses to test predicted genotypes. If time permits, students can germinate the F1 and parent generation seeds for comparison to their predictions. They may also perform actual plant crosses of the parent seeds and determine if the predicted phenotypes and genotypes from the Punnett squares are accurate.

Essential Question

How can monohybrid crosses be used to predict the genotypes and phenotypes of the parent generation?

Investigation Objectives

  1. Observe phenotypes for the F2 generation of Wisconsin Fast Plants®. Identify the genotypes of the F2 generation plants. Use monohybrid crosses to predict the genotypes and phenotypes of the F1 generation, and then of both parents, P1 and P2.

Next Generation Science Standards* (NGSS)

Science & Engineering Practices

Developing and Using Models

Disciplinary Core Ideas

LS3: Heredity: Inheritance and Variation of Traits

Crosscutting Concepts



Safety and Disposal

Ensure that students understand and adhere to safe laboratory practices when performing any activity in the classroom or lab. Use personal protective equipment such as safety glasses or goggles, gloves, and aprons when appropriate. Require students to adhere to all laboratory safety rules.


Dry plants out completely, place them in a resealable bag, and dispose of them in the trash. Plants may be allowed to continue to grow for additional investigations.

Student Procedures

  1. Place a filter paper or paper towel disk in the bottom of a petri dish. The paper should cover the dish’s bottom.
  2. Space the 10 seeds out evenly on the filter paper.
  3. Use the spray bottle to moisten the seeds and paper. The paper should be damp, but not sitting in a puddle.
  4. Cover the petri dish and place it under a fluorescent lamp.
  5. Observe the seeds daily for 4 or 5 days, or as directed by your teacher. Record your observations on the data sheet.
  6. Use the spray bottle to mist the seeds as needed. They should be kept moist, but not wet.

Teacher Preparation and Tips

  1. If you are using paper towels, cut them into disks to fit the bottom of the petri dishes prior to the activity. If the paper towels are thin, 2 layers may be necessary to keep the seeds moist.
  2. To save time, count out 10 seeds for each student or group before the activity.
  3. Check the petri dishes. Make sure seeds are separated and moist, but not standing in water. Place all seeds under intense fluorescent light for the duration of the investigation. Seeds should germinate in 2 to 3 days.
  4. Remind students to observe the seedlings carefully. They need to look at stem and leaf color. Color may change in intensity over time.

If students wish to perform the experiment they designed, have the additional seed packets available. The same germination technique may be used.

An alternative is to grow the parent generation through maturity and manually pollinate the parent plants, collect those seeds, and repeat the procedure for the F1 generation.

Seed Stock (Item Number) Genotype Phenotype Notes
Purple Stem, Hair (158810)
purple stem, sometimes extending to midribs of leaves; color varies from purple to dark pink
hair trait is quantitative and therefore best ignored in introductory activities
Non-Purple Stem, Hairless (158818)
anl/anl (recessive)
green stem
cross with 158810 for a monohybrid F1
Yellow-Green Leaf (158843)
ygr/ygr (recessive)
yellow-green leaves, purple stems
cross with 158810 for a monohybrid F1, or with 158812 for a dihybrid F1
Non-Purple Stem, Yellow-Green Leaf (158843)
anl/anl, ygr/ygr (double recessive)
yellow-green leaves, green stems
cross with 158810 for a dihybrid F1
Rosette-Dwarf (158815)
ros/ros (recessive)
very short plant
internodes do not elongate
Tall Plant (158825)
ein/ein (recessive)
tall, spindly plant
abnormally tall due to elongation of internodes
Petite (15833)
dwf1/dwf1 (recessive)
reduced height
mature at 5-15 cm; normal is 17-20+
Variegated (158820)
Var (non-Mendelian)
irregular leaf areas are devoid of chlorophyll
trait is part of the chloroplast genome, which is transmitted through the cytoplasm of the ovule; trait is not transmitted by pollen


Record the number of seeds germinated each day for 4 or 5 days, or as your teacher instructs. Identify the color of the stem for each seed germinated.

Day Number of Seeds Germinated Purple Stems Green Stems

Data will vary by group but should produce 75% purple stems and 25% green stems.

Analysis & Discussion

    1. What are the 2 possible stem phenotypes?

      Purple, hairy
      Non-purple, hairless

    2. Calculate the ratio and percentage for each phenotype.

      75% purple and 25% green

    3. Using your data, which phenotype appears to be dominant? Why?

      Purple, because of the greater percentage

    4. For each stem phenotype, identify the possible genotypes.

      Purple dominant, homozygous ANL/ANL and heterozygous ANL/anl
      Green recessive, homozygous anl/anl

    5. Using a monohybrid cross, predict the phenotypes and genotypes of the F1 generation plants

      ANL/anl × ANL/anl

ANL anl

Ratio of 3:1 purple to green given by the data, so both F1 parents were heterozygous purple, ANL/anl.


6. Using a monohybrid cross, predict the phenotypes and genotypes of the parent (P1 and P2) generation plants.


To produce heterozygous offspring, one parent must be homozygous dominant, ANL/ANL and the other must be homozygous recessive, anl/anl.


7. Design an experiment to test your predictions. (Check with your teacher about performing your experiment.)

Student answers will vary, but should include comparing phenotype counts for each generation of seeds. The specific phenotypes from each seed packet should be counted and compared to the ratios predicted by Punnett square crosses. The chi-square statistic may be introduced as an analysis tool now, since students will have actual seed phenotype data.

If time permits, you may begin with the P1 and P2 seeds and cross-pollinate the plants in class, harvest the seeds (F1 generation), and germinate those seeds. The same procedure can be used to test the crossing of F1 plants to identify F2 phenotypes and genotypes. This procedure will take several weeks.

Shop the Kit

Use evidence gathered from observations and data collection to explain an inheritance pattern. Infer from observation how genes code for the purple stem trait expressed in Fast Plants®. Develop a model that shows how traits are inherited over several generations.
Wisconsin Fast Plants® 72-Hour Monohybrid Genetics Kit


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