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Introduction to Phenotypes with Wisconsin Fast Plants®

Carolina Labsheets™

In this lab, students germinate seeds of Wisconsin Fast Plants and examine the plants that grow from them for differences in appearance. This introductory-level activity can be used as a pre-lab to a unit on Mendelian genetics, and assumes that students are familiar with the terms genotype, phenotype, and allele. This activity also can serve as an engaging introduction to variation within a species. The Confetti Seed Mix (158695) recommended for the activity contains a mixture of the seed types described in the table below. Alternatively, you can substitute the Wisconsin Fast Plants Genetic Seed Sampler (158800) for the Confetti Seed Mix; it contains one packet of each seed included in the Confetti Seed Mix.


Student Lab Sheet

Seed Stock (Item Number) Genotype Phenotype Notes
Purple Stem, Hairy (158810) ANL/ANL (dominant) YGR/YGR ROS/ROS EIN/EIN DWF1/DWF1 purple stem, sometimes extending to midribs of leaves; color varies from purple to dark pink hairy trait is quantitative and therefore best ignored in introductory activities
Non-Purple Stem, Hairless (158812) anl/anl (recessive) green stem cross with 158810 for a monohybrid F1
Yellow-Green Leaf (158818) 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 (158833) 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


Needed Materials*

Wisconsin Fast Plants Confetti Mix Seed, pack of 100 (158695)

Wisconsin Fast Plants Growing Instructions booklet (included with most Fast Plants kits)

Fast Plants growing materials, including:

quads (158960)

quad wicks (158978)

soil (158965)

fertilizer pellets (158970)

watering pipets

watering system (158974)

plant stakes with rings (158984; to keep tall plants from falling over)

plant labels (158982)

lighting system, e.g., Plant Light House® (158994) or Plant Light Bank (158999)

paper towels

beakers or cups for water

plastic spoons

scissors

sinks, large cups, or trays


Important:
Do not use standard potting soil with Fast Plants. Use of these mixes often results in non-germination of seeds. Our 158692 Wisconsin Fast Plants Confetti Kit comes with the Confetti Seed Mix and the Wisconsin Fast Plants growing materials. You can also use our classroom-sized 158993 Wisconsin Fast Plants Growing System or the growing materials from one of our other Wisconsin Fast Plants kits.

Optional Materials
Students will need rulers if they decide to measure plant height. Magnifiers (hand lenses) and dissecting microscopes can be used to examine the seeds and seedlings. Seeds that give rise to Non-Purple Stem plants will be paler than other seeds. Small cups can be used to distribute the fertilizer pellets and seeds (separately).


Safety

Ensure that students understand and adhere to safe laboratory practices when performing any activity in the classroom or lab. Demonstrate the protocol for correctly using the instruments and materials necessary to complete the activities, and emphasize the importance of proper usage. Use personal protective equipment such as safety glasses or goggles, gloves, and aprons when appropriate. Model proper laboratory safety practices for your students and require them to adhere to all laboratory safety rules.


Procedures

Students can work individually or in groups of 2 or 4 per quad.

Moisten the potting soil at least an hour before the lab is to begin.

Cover work surfaces with paper towels or sheets of newspaper, because filling the quads with soil can be messy.

If you do use cups to hold the fertilizer pellets and seeds, count out 12 pellets into each fertilizer cup and 8 seeds into each seed cup. Have all materials available for easy pick-up.

Planting Seeds
Check your lighting system to be certain it is operating properly.

Set up the watering system. (Consult the Wisconsin Fast Plants® Growing Instructions booklet for directions.) First, fill the watering tray reservoir with water, and drop in two anti-algal squares. Attach the platform lid to the reservoir. Saturate a water mat and lay it on the lid, with the end of the mat extending into the water in the reservoir. Make sure the mat is thoroughly wet. When placed on the mat, the wick protruding from the bottom of each quad will draw water from the mat into the quad, and from there into the soil.

Each student (or group) will need the following materials:

quad
4 wicks
12 fertilizer pellets
8 Confetti Mix seeds
beaker or cup of water
watering pipet

Observing Differences in Phenotype
Provide students with access to their quads, and have them observe their plants 2 or 3 times between Day 4 and Day 10 after planting (e.g., Day 4, Day 7, and Day 10). The activity can be concluded on Day 10. Allow time for the students (or groups) to compare and contrast their plants. Projecting images of the plants on an interactive whiteboard or similar device can help students make these comparisons.

Optional: A shorter version of this lab can be completed in 3–5 days by germinating the seeds on absorbent paper (e.g., filter paper or paper towels) in petri dishes and examining the seedlings. Intense fluorescent light is required. The phenotypes of purple and green (non-purple) stems and green and yellow-green leaves will be obvious. Students also will see variation in the stem length of the seedlings, although, this will not be as obvious as with mature plants. Students might be able to distinguish the tall plants and the rosette-dwarf seedlings from those of normal height.

Students can continue to grow the plants, cross-pollinate them, and germinate the F1 seeds to determine which phenotypes are due to dominant alleles. They can intercross the F1 plants to produce an F2 . Note that Wisconsin Fast Plants are self-infertile—that is, pollen must be transferred between the flowers of two separate plants to produce viable seeds. Transferring pollen between flowers on the same plant will not work. In the F2 of a cross involving rosette-dwarf, the homozygous recessive seeds (ros/ros) will be dormant and will not germinate. In crosses involving variegated plants, students should make sure to record which plant donates the pollen and which receives the pollen.


Answer Key to Questions Asked on the Student LabSheet

Students’ answers may vary. Sample answers are provided below.

Observe your Fast Plants according to the schedule set by your teacher. Study and compare the phenotypes of your plants. Also, compare your plants to plants grown by other students or groups. At the end of the observation period, summarize the different phenotypes you have identified.

  1. Some plants have purple or red stems [Purple Stem, Hairy] while others have green stems [Non-Purple Stem, Hairless; Non-Purple Stem, Yellow-Green Leaf*].
  2. Some plants are tall and spindly and fall over [Tall Plant].
  3. Some plants are shorter than others [Petite].
  4. Some plants are pale green or yellow [Yellow-Green Leaf; Non-Purple Stem, Yellow-Green Leaf*].
  5. Some plants have no stems. Their leaves lay flat on the soil [Rosette-Dwarf].
  6. Some plants have white areas where there is no color [Variegated].

*Some students may make a separate listing for the double mutant.

Choose one of the phenotypes from your list and record a description of it here:
Green Stem

How could you determine whether this phenotype is inherited?
Cross a green stem plant with another green stem plant. Harvest and plant the seeds. If the plants that grow from these seed have green stems, the phenotype is inherited. If some of the plants have purple stems, then the green stem phenotype may not be inherited, and more study is needed.

If the phenotype is inherited, how could you determine if it is inherited through a dominant or a recessive allele?
Cross a green stem plant with a purple stem plant. Harvest, and plant the seeds. If the allele for green stem is dominant, then all the plants will have green stems. If the plants have purple stems, then the allele for green stem must be recessive.


Student Lab Sheet



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