Using Genetic Crosses to Analyze a Stickleback Trait

Howard Hughes Medical Institute
Type Category
Instructional Materials
Lesson/Lesson Plan , Activity
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



In this HHMI Biointeractive hands-on activity, students use photos of stickleback fish to analyze the results of genetic crosses between fish with different traits.  Students are introduced to the activity through a suggested video: "Students should watch the short film Evolving Switches, Evolving Bodies before doing this activity. You may consider showing the film up to the point where Dr. David Kingsley describes how genetic crosses using stickleback fish were done (4 min. and 45 sec. after the start of the film). You could stop the film at that point, have the students complete this activity, and then finish showing the film." p.2 of Teacher Materials. Students are asked to classify fish according to the presence or absence of pelvic fins, use Punnett squares to predict frequencies of genotypes and phenotypes, make a claim about the mode of inheritance and to evaluate evidence to justify their claim. Teachers can extend the activity by asking students to use chi-square to evaluate data and provide students with the opportunity to experiment with ideas about determining genotypes with their own test crosses. This activity is supported by a video, a Teacher Guide, a Student Handout, and the required fish pictures which may all be downloaded from the website.


Intended Audience

Educator and learner
Educational Level
  • Grade 12
  • Grade 11
  • Grade 10
  • Grade 9
Access Restrictions

Free access - The right to view and/or download material without financial, registration, or excessive advertising barriers.

Performance Expectations

HS-LS3-3 Apply concepts of statistics and probability to explain the variation and distribution of expressed traits in a population.

Clarification Statement: Emphasis is on the use of mathematics to describe the probability of traits as it relates to genetic and environmental factors in the expression of traits.

Assessment Boundary: Assessment does not include Hardy-Weinberg calculations.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
Students need prior knowledge of genetic vocabulary and completing and analyzing Punnett squares. Teachers can assign independent practice Punnett square review activities to students before starting this activity. The teacher’s guide suggests students watch the short film Evolving Switches Evolving Bodies ( before doing the activity. The film describes how the researchers collected the genetic crosses data provided in the students' handout. Students can also analyze additional research data ( provided in the activity as an extension activity.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
This activity supports the practice of analyzing data by asking students to make predictions of F1 and F2 fish crosses. Students collect data on the ratio of stickleback with pelvic spines and stickleback without pelvic spines. Students do calculations and predictions of probability on what they expect for subsequent generations. Teachers can extend the lesson and provide additional support of the practice by asking students to use a chi-square analysis to justify their claim. The Biointeractive website ( has a math and statistical teacher guide that can provide teachers with additional implementation support. A College Board’s publication, AP Biology Quantitative Skills: A Guide for Teachers, provides more extensive background on quantitative concepts in biology, including SEM." Link:

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
Students sort fish cards into two groups based on the presence or absence of pelvic fins. They make a claim about whether a phenotype is dominant or recessive. They collect data to support their claim by analyzing F1 and F2 fish cards. The student handout provides additional experimental data to help students justify their claim. Teachers can implement the full Discipline Core Idea by introducing students to the exciting field of epigenetics. Epigenetics is the study of how environmental factors influence the expression of genes. An epigenetics teaching module can be found on the Learn Genetics website ( After completing some of the lessons in the modules, teachers can lead students in a whole-class discussion on how they think environmental factors affect stickleback phenotypes.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
Teachers need to model data analysis techniques and provide additional activities for students struggling with the mathematical and statistical components of this activity. When students are calculating the ratios, considering probabilities, and making predictions about the outcomes of traits in future generations, they are basing their thinking on mathematics.

Resource Quality

  • Alignment to the Dimensions of the NGSS: This activity provides opportunities to engage students in three-dimensional learning by asking them to use their prior knowledge of Mendelian genetics to predict the frequencies of genotype and phenotypes in an offspring of stickleback fish, develop hypotheses, analyze data, and evaluate evidence to support the problem.

  • Instructional Supports: This activity engages students with an authentic phenomenon using pictures of research specimen to obtain data on the presence or absence of pelvic fins in stickleback fish. Students use mathematical thinking to develop hypotheses about whether a phenotype is dominant or recessive. The detailed student handout is divided into three parts and extension activities that supports multiple practices throughout the lesson. The lesson that can be completed in one 50-minute class period and as a homework assignment. The teacher’s guide provides an overview of the activity, curriculum connections, suggested timeline and audience. A detailed list of teaching tips and answer key are also provided.

  • Monitoring Student Progress: The student handout provides many opportunities to apply critical thinking skills rather than rote memorization that are sometimes used to teach genetic principles. However, teachers need to rotate around the classroom and use observational and questioning strategies to check for understanding and monitor students throughout the activity. After completing the activity, teachers can assign the enrichment activities to further explore the genotype-phenotype connection.

  • Quality of Technological Interactivity: This is not an interactive, technology-based resource, although the links to supporting video and to the original research article do enhance the value of the resource.