Teacher Notes

Mendel’s laws are the core ideas in biology education and the first set of concepts students learn about heredity and inheritance. However, these concepts are often taught as facts. Students are told about Mendel’s story and ideas without being provided the experience to reasoning about inheritance patterns like scientists.

Use this model to explore Mendelian inheritance in sunflowers like a scientist. Explore how three phenotypes are inherited and test your hypotheses instantaneously, and apply the knowledge to create new purebred varieties.

Grades: 6-12, College introductory biology
NGSS Standards: MS-LS3-2

HOW IT WORKS

Model Rules

Three genes are involved. Each gene determines one character.

Y --> floral color; S --> inflorescence type; C --> disc color

Only complete dominance is involved.
Gametes are produced based on the parent sunflowers, following the laws of segregation and independent assortment.
In self-pollination, gametes randomly fused to form offspring.
In cross-pollination, the gametes of one parent sunflower will randomly fuse with the gametes of the other parent sunflower.
The number of offspring slightly varies in each generation.

Sunflowers vary in color, inflorescence, and disc color. Image from Cvejić et al. (2016)

THINGS TO NOTICE

This model is created based on the studies from Cvejić et al. (2016) and Divita et al. (2012), which have suggested that the genes of floral color and inflorescence type are inherited independently. In this model, it is assumed that disc color is also inherited independently in relation to the floral color and inflorescence type.
Depending on the cases, a number of gametes containing three alleles, one for each of three genes, are first produced and then randomly fuse to form sunflowers. Therefore, the sunflowers you get at the beginning can be either heterozygous or homozygous. You will not be informed about the dominance and recessiveness of the presented traits. WHAT?!!! Yes, let’s face this and keep two things in mind: 1) scientists do not just get purebred individuals automatically, and 2) they don’t just know which trait is dominant or recessive. They have to figure them out! This model allows you to work like a scientist to figure out the dominance and recessiveness of floral color, inflorescence type, and disc color in sunflowers.
When you conduct a test cross, the number of offspring slightly varies in each generation. Combining the random fertilization of gametes, you are unlikely always to get the ratios that perfectly match the theoretic ones. This situation mimics the authentic studies, in which scientists rarely get perfect numbers but focus on identifying data patterns.

HOW TO USE IT

Choose one of the seven cases.
Press on “Start/reset Simulation” button to confirm.
Click on “Press and choose flower(s)” button.
Now use cursor to choose sunflower(s) in the simulation window.
You may choose one sunflower to conduct self-pollination, or choose two flowers to conduct cross-pollination.
Examine offspring sunflower frequencies in “Progeny” section.

TEACHING SUGGESTIONS

Vase with Twelve Sunflowers （Vincent van Gogh 1888）

See the detailed Teacher's Guide here.

Engage

Present the large number of variations in sunflowers using images and even some famous artwork, e.g., the sunflower series from Vincent van Gogh. Use real sunflowers if possible. Let students observe the images and identify different traits in sunflowers. Prompt students to ask questions regarding the inheritance of these traits.

Explore

Let students explore the inheritance of floral color, inflorescence type, and disc color using the simulation. Focus on observing the phenotype inheritance patterns. E.g., what color do the offspring sunflowers display when a yellow sunflower crosses with a lemon-yellow sunflower? Have students record their predictions and simulation results in a science notebook. At the end of the class, let students share their results and discuss what causes the inheritance patterns.

Explain

Introduce terminology and Mendel's law through a short lecture or reading. Let students connect the terms, such as dominant, recessive, gene, allele, trait, etc., to the above investigation. Ask students to use Punnett square to explain their observations and data from the simulation. The teacher may reveal sunflower genotypes in the simulation and invite students to predict phenotypes and genotypes of the next generation.

Extend

The simulation provides three cases of monohybrid and three cases of dihybrid. Teachers may use some of these cases to help students learn about Mendel's law, and use other cases to extend student learning. High school students and college students may be asked to collect numeric data from the simulation and then perform chi-square goodness of fit tests to analyze the data.

Evaluate

Students should be able to identify the dominance and recessiveness of floral color, inflorescence type, and disc color and provide explanations supported by the evidence from the simulation.

Students may be asked to create new purebred varieties: Teddy bear and White Nite, and construct a written explanation.

Exploring inheritance Patterns

Sunflower Inheritance Data collection Tables- Explore Patterns

Determining dominant and recessive traits

Sunflower Inheritance Data collection Tables- Determine dominant and Recessive Traits

CREDITS

Dr. Lin Xiang creates this module at the University of Kentucky. If you mention this model in a publication, we ask that you include the citations below.

Xiang, L. (2022). Mendelian inheritance in sunflowers. Department of STEM Education, University of Kentucky, Lexington, KY.

REFERENCES

Cvejić, S., Jocić, S., & Mladenović, E. (2016). Inheritance of floral colour and type in four new inbred lines of ornamental sunflower (Helianthus annuus L.). The Journal of Horticultural Science and Biotechnology, 91(1), 30-35.

Divita, M. E., Salaberry, M. T., Echeverría, M. M., & Rodríguez, R. H. (2012, February). Genetic and environmental effects of some traits of ornamental value in sunflower (Helianthus annuus L.). In Proc. 18th Int. Sunflower Conf., Mar del Plata (pp. 566-574).

Questions? Comments? Email us.

Page updated

Google Sites

Report abuse