What Is a Genotype? Understanding Genes and Inheritance
A genotype is the genetic makeup of an organism — the specific combination of genes it carries from both parents.
For middle school students, understanding the concept of genotype helps unlock how traits are inherited and why siblings can look so different. In this article, we’ll explore what a genotype is, how to teach it visually, and how JoVE videos and hands-on activities can make it stick.
What Does Genotype Mean? A Breakdown for Middle School Students
Let’s break down what is a genotype for middle school students in simple terms:
A genotype is the pair of alleles (gene versions) that determine a specific trait — like TT, Tt, or tt for plant height.
Each letter represents one allele from each parent. These combinations control the instructions your body follows to build traits.
JoVE’s concept videos help show these combinations forming during fertilization, linking the abstract idea of genes to something students can see.
Genotype vs Phenotype: What’s the Difference?
Many students confuse genotype vs phenotype, so make the distinction clear:
- Genotype = the gene combination (e.g., Tt)
- Phenotype = the physical trait you can see (e.g., tall plant)
Here’s an easy analogy:
- Genotype is the recipe
- Phenotype is the cake
Use visuals to reinforce that different genotypes (TT and Tt) can result in the same phenotype — but only the genotype reveals the underlying genes.
How Do Allele Pairs Form Genotypes?
It starts during reproduction. One allele comes from each parent. The pair forms a genotype, and that genotype decides how a trait is expressed.
For example:
- T + T = TT → dominant trait shows
- T + t = Tt → dominant trait still shows
- t + t = tt → recessive trait shows
Teaching this visually is key. Use colored cards, base blocks, or JoVE videos that model allele combinations in a step-by-step process.
Predicting Traits in Offspring Using Genotypes
Once students understand genotypes, they can start predicting traits in offspring using Punnett squares.
Try this example:
- Parent 1: Tt (tall)
- Parent 2: Tt (tall)
- Possible genotypes: TT, Tt, Tt, tt
- Phenotypes: 3 tall, 1 short
This shows how dominant and recessive alleles affect outcomes. It’s also a perfect setup for exploring genotype vs phenotype deeper.
Visual Activity to Teach Genotype Combinations
Here’s a quick visual activity to teach genotype combinations:
“Allele Match” Simulation
Materials: Colored paper cards with T and t
Instructions:
- Students draw one card from each of two cups
- Combine to create genotypes (e.g., Tt)
- Record results and sort by phenotype
Extend it with class data collection to graph trait ratios and discuss why some traits appear more often than others.
This leads directly into your classroom Punnett square lesson on genotypes — combining modeling with real data.
Conclusion: Teaching Genotype the Visual Way
Understanding genotype helps students decode the hidden instructions that shape life. With simple terms, real-life examples, and JoVE-powered visuals, this lesson becomes not just clear — but engaging.
🎓 Book a Free Demo to access JoVE’s complete collection of videos, Punnett square lessons, and NGSS-aligned activities for teaching genotype and inheritance in middle school classrooms.
Bring JoVE to your classroom starting as low as $2 per student.*
Explore funding resources to learn how your school can start using JoVE’s complete STEM video library today.
*Pricing based on 1,500 students.
