Yakima WATERS Mini Lesson
Hormones & Heredity - Comparing Dwarf Peas to Normal Peas
Targets and Assessment
WA Science Standards Addressed:
Science 9-12 INQB Inquiry investigation
Science 9-12 INQC Inquiry explain
Lesson Parameters
Content Area: Genetics and Cell Growth
Overview: Students will learn that there is a genetic
difference between dwarf and standard peas even though
they are the same species. They will realize a specific allele
is responsible for the height of the plant and it can be
turned on using the hormone gibberellin.
Grade Level: 10
Assessments:
 Formative assessment was conducted by
observing and questioning students during the
lesson
 Students were given credit for participation since
no lab write-up was expected for this activity.
Suggested Time: 50
Special Materials:
 Gibberellin Solution (100 u/mL)
 Dwarf and Normal Pea Plants (Pissum sativum)
Learning Outcomes:
 Knowledge: Students will be able to explain how hormones can interact with alleles to change the
genetic variation within an organism.
 Skill: Students will be able to apply their knowledge to determine if the hormone gibberellin has the
same effect on dwarf and normal pea plants.
Science Concept Background:
Gibberellin is a common growth hormone found in plants. There are more than 200 variations of this
hormone and most are important for plant growth. The application of Gibberellin (especially near the apical
meristem) can increase the growth of certain plants by affecting the alleles that code for height.
Humans have been able to domesticate several species of plants by breeding them for certain traits that
would otherwise be rare in the wild population. This allows us to produce fruits and vegetables that are
specific colors, grow larger, and smell different than the wild population. Several species of plants including
domesticated corn and peas have dwarf variations that have been bred to preserve their shortened stature.
Since Gibberellin is a natural growth hormone found in plants, adding large concentrations of it to dwarf
plants can increase their height. On the other hand, adding Gebberellin to normal height plants doesn’t affect
them suggesting the increase of this hormone directly affects the allele that differentiates dwarf plants from
normal height plants.
Materials:
 Dwarf Pea Plants
 Normal Pea Plants
 Gibberellin Solution (10 ppm)
 Spray Bottle
 Ruler
Procedure:
Key questions:
What makes plants grow?
Why are dwarf peas shorter than normal height peas?
Is there a way to test the effects of growth hormones on peas?
1. On first day of experiment discuss the presence of plant hormones and why gibberellin in particular is
important for plant growth.
2. Show students planted peas and talk about how the Little Marvel and Alaskan peas are different
variations of the same species, which grow differently based on their genetic makeup. This would be a
good time to talk about selecting plant varieties and growing them to accentuate specific traits
(example: height, fruit color and size, etc.).
3. Explain to students how we are going to spray one tray of peas every day with the gibberellin hormone
and record if there is a change in these treated plants versus the other tray of plants that will act as a
control.
4. Have volunteers spray plants every day and once a week have whole class compare the changes.
5. At the end of two weeks have students analyze their data and determine how gibberellin affects the
two varieties of peas.
Extension(s):
 Leave time at the end of class for a group discussion about how applying gibberellin to the pea
plants has changed their ability to grow. See if students make the connections between this
growth hormone only affecting the little marvel peas and what this must mean about the
differences between this variation of peas compared to the Alaskan peas.
Teaching Tips:
 Sprout seeds a week or two before starting experiment. Plant peas in two trays. Divide both in
half and plant little marvels on one side and Alaskan peas on the other side of each tray.
Supplements:
 Plant Growth Regulators. 1983. Carolina Biological Supply Company. Burlington, NY.
Author: Jennifer Lannoye, Yakima WATERS Project, CWU, 2009-2010