Introduction to Heredity and Traits

Five easy-to-implement classroom activities teach the basics of heritable traits. Three take-home activities help students share what they're learning with their families.

Suggested Implementation

Below is a suggested sequence for implementing the activities contained in the unit. Please see each individual activity for implementation instructions, suggestions for adaptations and extensions, and applicable standards.

Day	Activity	Notes
Day 1 (40 mins.)	An Inventory of My Traits	Students take an inventory of their own easily-observable genetic traits and compare those inventories with other students in groups.
	Observable Human Characteristics	This web page shows many of the traits included in An Inventory of My Traits.
	A Tree of Genetic Traits	Students find the most and least common combination of traits in the class by marking their traits for tongue rolling, earlobe attachment, and PTC tasting on paper leaf cut-outs. Students then organize the leaves on a large "tree of traits."
	Family Traits Trivia (Homework)	Students use game cards to inventory the traits in their family. (Note: individuals in families do not need to be related to participate in this activity.)
Day 2 (40 mins.)	Generations of Traits	Students track and record the passage of colored "pom-pom traits" through three generations of ginger-bread people.
	Traits Bingo	In this review activity, students cross off or color bingo squares in response to questions about their traits.
	Handy Family Tree (Homework)	Students distinguish between inherited and learned traits by creating a "family tree of traits" using handprints. (Note: Individuals in families do not need to be related to participate in this activity.)
Day 3 (40 mins.)	A Recipe for Traits	Students learn that differences in DNA lead to different traits by: 1) randomly choosing strips of paper that represent DNA, then 2) decoding the DNA strips to complete a drawing of a dog.
Day 3 (40 mins.)	Family Traits and Traditions (Homework)	Students and their families play a matching game with cards to identify traits that are inherited and traits that are learned or passed on through tradition.

An Inventory of My Traits

Students take an inventory of their own easily observable genetic traits. Working in small groups, they observe how their trait inventories differ from those of others. Students record their observations in a data table and make a bar graph to show the most and least common traits in the group.

Learning Objectives

Traits are observable characteristics that are passed down from parent to child.
An individual will have many traits they share in common with others.
An individual's overall combination of traits makes them unique.
Some traits are more common in a population than others.

An Inventory of My Traits (PDF)

A Tree of Genetic Traits

Students mark their traits for tongue rolling, PTC tasting (a harmless, bitter chemical), and earlobe attachment on tree leaf cut-outs. They then place their leaves on a large tree whose branches each represent a different combination of traits. When completed, the tree forms a visual representation of the frequency of trait combinations within the class.

Learning Objectives

Traits are observable characteristics that are passed down from parent to child.
An individual will have many traits they share in common with others.
An individual's overall combination of traits makes them unique.
Some traits are more common in a population than others.

A Word About PTC Safety

The 2004 publication Investigating Safety: A Guide for High School Teachers by Texley et al. has raised an alarm in the teaching community about the usefulness and safety of PTC taste testing. This has led to PTC being banned from many schools and districts - we believe unnecessarily.

Yes, PTC is toxic. In rats, the most sensitive animals tested, the oral LD50 of PTC (the amount that killed 50% of test animals) is 3 mg/kg. However, PTC is so intensely bitter that tasters can detect it in miniscule quantities. A single test paper from Carolina Biological Supply contains just 0.007 mg of PTC. And the amount that is licked off the paper by a test subject is much less than this. In addition, there has not been a single report of toxicity arising from PTC taste testing, which has been performed on tens of millions of individuals worldwide. To put the toxicity of PTC into perspective, we offer this quote (from Merritt et al., Am. Biol. Teacher online 70:4):

There is no question that PTC is toxic (LD50 in rat is 3mg/kg, in mouse 10mg/kg, and in rabbit 40mg/kg), but so is table salt (acute toxicity in humans at 500-1000mg/kg). The issue is how much PTC is on a taste paper. Texley et al. indicate that “a single strip contains about 0.3 mg” but the two suppliers we checked with indicate that a taste paper contains either 0.007 mg (Carolina Biological Supply Company) or 0.005 - 0.007 mg (ScienceStuff). Assuming a linear dose response curve, we calculate that the 230 mg of NaCl in a vending machine bag of potato chips is about 100 times more toxic than the 0.007 mg of PTC in a taste paper. We do not believe there is any reason for teachers to be concerned about the toxicity of PTC taste papers.

Full Instructions (PDF)

Choose either english versions...

Then download the leaves page and one of the following tree files...

Or english/spanish bilingual versions...

Then download the leaves page and one of the following tree files...

Family Traits Trivia

Take home game using picture cards that identify traits. A family or group can use this activity to see which traits they have in common.

Family Traits Trivia (PDF)

Generations of Traits

In this hands-on activity students track and record the passage of colored "pompom traits" through three generations of ginger-bread people. In doing so, students learn that traits are passed from parents to offspring and that siblings may or may not receive the same traits from their parents.

Learning Objectives

Traits are observable characteristics that are passed down from parent to child.
An individual will have many traits they share in common with others, and more so with siblings and parents.
An individual's overall combination of traits makes them unique.
An equal number of traits are passed on from each parent.

Generations of Traits (PDF)

Traits Bingo

Students cross off or color bingo squares in response to questions about their traits. This activity is designed to be used as a review following An Inventory of My Traits, Generations of Traits, and A Tree of Genetic Traits.

Learning Objectives

Students will inventory their own inherited traits.
Students will compare traits to determine which are most and least common in the class.

Traits Bingo (PDF)

Handy Family Tree (Homework)

An activity to catalog a family's traits on a tree made of stacked handprints.

Handy Family Tree (PDF)

A Recipe for Traits

Students create and decode a "DNA recipe" for man's best friend to observe how variations in DNA lead to the inheritance of different traits. Strips of paper (representing DNA) are randomly selected and used to assemble a DNA molecule. Students read the DNA recipe to create a drawing of their pet, and compare it with others in the class to note similarities and differences.

Learning Objectives

Every organism inherits a unique combination of traits.
DNA is a set of instructions that specifies the traits of an organism.
Variations in the DNA lead to the inheritance of different traits.

A Recipe for Traits (PDF)

Family Traits and Traditions (Homework)

A memory match game in which participants must discern the differnce between a trait that is inherited or one that is learned/environmental.

Family Traits and Traditions (PDF)