Part 1: Engage (Anchoring Phenomenon)

Phenomenon: Imagine two parent creatures that both have purple fur and blue eyes. They have a baby, and surprisingly, the baby is born with yellow fur and red eyes! How can two parents with the exact same physical appearance have offspring that look completely different from them? Furthermore, why does this happen predictably in some cases, but occasionally, an entirely unexpected variation appears?

Discuss:

1. Based on your prior knowledge, how are traits passed from parents to offspring?
2. What “need to know” questions do you have about how offspring inherit traits and why variations occur?

Part 2: Explore (Simulation Investigation)

Simulation: DNA and Population Inheritance Model

In this simulation, you will observe the inheritance of two traits: Fur Color and Eye Color.

• Fur Color: Purple (B) is dominant, Yellow (b) is recessive.
• Eye Color: Blue (E) is dominant, Red (e) is recessive.

Procedure:

1. Baseline Observation: Set both the Mother and Father to be heterozygous for both traits (Bb Ee). This means they carry both dominant and recessive alleles. Observe their phenotypes (appearance).
2. Mendelian Inheritance Trial: Set the “Mutation Rate” to 0%. Set “Number of Offspring (Trials)” to 1000. Click “Run Population Trial”.
3. Record Data: Record the number of offspring in each phenotype category in Data Table 1.
4. Environmental Impact Trial: Change the genotypes of both parents to homozygous recessive (bb ee). Run a trial with 1000 offspring and a 0% Mutation Rate. Observe the results.
5. Mutation Trial: Keep the parents at bb ee. Increase the “Mutation Rate” to 15%. Run a trial with 1000 offspring. Record the results in Data Table 2.

Data Table 1: Dihybrid Cross (Bb Ee x Bb Ee, 0% Mutation)

Data Table 2: Homozygous Recessive Cross with Mutation (bb ee x bb ee, 15% Mutation)

Part 3: Explain (Sensemaking)

1. Analyzing the Data: Look at your data from Data Table 1. Does the offspring population show a predictable pattern of inheritance? Explain how the offspring can have traits (like yellow fur or red eyes) that neither parent physically displays.
2. The Role of DNA: What is the relationship between the DNA (genes and alleles on the chromosomes) of the parents, the proteins produced, and the resulting physical traits (phenotypes) observed in the offspring?
3. The Impact of Mutations: Compare your results from Step 4 and Step 5 in the Explore phase. How did the environmental mutation rate affect the genetic certainty of inheritance? Explain the cause-and-effect relationship between a mutation during meiosis and the physical trait of the offspring.

Part 4: Elaborate/Evaluate (Argumentation & Modeling)

Task: Formulate a scientific question and use the simulation as a model to gather evidence to answer it.

1. Formulate a Question: Write an empirically testable question about the role of DNA, inheritance, or mutations in determining the traits of a population. (e.g., “How does changing one parent from heterozygous to homozygous dominant affect the frequency of recessive traits in a population?”)
2. Investigate: Use the simulation to gather data that can answer your question. Record your parents’ genotypes, your mutation rate, and your population results.
3. Construct an Explanation: Write a short paragraph explaining the results of your investigation. In your explanation, explicitly connect the structure of DNA (alleles on chromosomes) to the cause-and-effect patterns of trait inheritance you observed. Discuss how the model (simulation) helped clarify this relationship.

Teacher Notes & Alignment

This task is designed to align with the NGSS High School Life Sciences performance expectation HS-LS3-1: Ask questions to clarify relationships about the role of DNA and chromosomes in coding the instructions for characteristic traits passed from parents to offspring.

Three-Dimensional Alignment:

• Science and Engineering Practice (SEP): Asking Questions and Defining Problems. Students formulate testable questions based on the DNA simulation model in Part 4.
• Disciplinary Core Idea (DCI): LS1.A: Structure and Function & LS3.A: Inheritance of Traits. Students explore how genes code for proteins/traits and how these traits are inherited.
• Crosscutting Concept (CCC): Cause and Effect. Students analyze the causal relationship between gene sequence (including mutations) and population phenotypes.

Evidence Statements Addressed:

1. Students construct an explanation that includes the idea that regions of DNA called genes determine the structure of proteins.
   • Student Work Demonstration: In Part 3 (Question 2), students explicitly describe this relationship.
2. Because all cells contain DNA, all cells contain genes that can code for the formation of proteins.
   • Student Work Demonstration: This is fundamental to their explanation of how offspring inherit traits from their parents’ chromosomes.
3. Students use models of DNA to formulate questions, the answers to which would clarify cause and effect relationships.
   • Student Work Demonstration: In Part 4, students formulate a question about inheritance and test it using the simulation model.