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Genetics

Fly Chromosomes
Digital Teaching Box
Genetics
Genetics

Why is there so much variation within families? Why don’t siblings with the same biological parents look identical to each other? This Digital Teaching Box contains classroom-tested, NGSS-aligned resources for teaching the sources of genetic variation and how traits are inherited.

Grade Level & Course
9th–10th grade biology

Author & Affiliation
Daisy Yeung
Teacher-in-Residence
Exploratorium Teacher Institute

Time Estimate
Four weeks

Concepts Covered
Mendelian genetics
Molecular genetics
Genes x environment

NGSS Alignment


Resource 1: Developing an Initial Model to Explain Genetic Variation Within Families

Through group activities and class discussions, give students the chance to observe genetic variation in biological families and begin to draw initial models of what might cause it.

Resource Link

Resource Attribution
Exploratorium Teacher Institute

Resource Type
Classroom Activity

Teaching Notes

This is the anchoring phenomenon for the whole unit. As such, student groups should return to these models and update them at least once at the end of the unit, and preferably another time halfway through. Ways in which students can make their changes more explicit can be found here.

As students are investigating the family photos, be open to any background information they bring in. Accept all noticings with no judgement. Discussion questions might include:

  • What do you notice?
  • What are the similarities between parents and offspring? What are the differences?
  • What questions do you have?

As student groups are drawing out their initial models, circulate the room and ask probing questions to elicit more of their ideas. For example, if students choose to connect ideas with arrows, ask them to explain what the arrows mean or give them labels to explain their meaning.

Initial models are meant to be incomplete, so it’s important to provide time for students to ask questions. What do they want to investigate in order to better answer the question? What information do they feel is missing to complete their model?

Resource 2: Skin Color Spectrum

Focus students’ investigation into variation on one particular complex trait: skin color. Students compare the skin colors of their inner and outer arms and discuss what could be causing any variation they observe.

Resource Link

Resource Attribution
Exploratorium

Resource Type
Image, Classroom Activity

Teaching Notes

Most human traits are not controlled by single genes, but by multiple genes and alleles combined with multiple environmental factors. Many genetics units begin with a survey of human traits that are supposedly Mendelian, that is, controlled by single genes and presented as binary (attached vs. free earlobes, blue vs. non-blue eyes, freckles vs. no freckles). I suggest that starting a genetics unit with a complex trait that involves multiple genes and alleles with both genetic and environmental factors is a more scientifically accurate representation of the inheritance patterns of most traits in living things, may help students avoid the commonly held misconception that most traits are Mendelian, and may help students appreciate and consider the significant environmental effects that contribute to most human traits.

Since this is an introductory activity to help frame the unit, accept all ideas without judgement.

Cut the colored image into strips (A–F) and fasten together with a brad. Have students identify which swatches best match the colors of their inner upper arms and the colors of their outer lower arms.

Discussion questions:

  • What did you notice?
  • Did your skin color change by number or by letter or both?
  • Are there any patterns of change within the class?
  • What do you think causes your inner arm to be that particular color?
  • What do you think causes your outer arm to be that particular color?
  • Why might some people have a greater difference between the two? Why might some people have no difference between the two?
    • This will hopefully get at the idea that skin color has both genetic and environmental components, which ties in with the next activity.

Resource 3: Genetics vs. Environment Spectrum

In an extension of Resource 2, continuing the framing for the unit, students discuss which traits they believe to be caused more by genetic factors, which are caused more by environmental factors, and which are a combination of both.

Resource Link

Resource Attribution
Modified from BetterLesson: Nature vs Nurture spectrum activity

Resource Type
Classroom Activity

Teaching Notes

This framing activity helps to elicit student ideas about what causes variations in humans. Accept all ideas without judgement.

Six to eight different traits is a good number to promote discussion. When choosing the traits you want to discuss, think about which ones are appropriate for your students. It’s best to tailor the list to the backgrounds and interests of your students.

Discussion questions:

  • What do you notice?
  • Can you tell me why you decided to place your dot there?
  • Are there any similarities between the more “genetic” traits and the more “environmental” traits?
  • Think about the model you drew earlier—are there any variations you see that may have an environmental factor? How would you know?

Resource 4: Mendelian Genetics Introduction Videos

Introduce Gregor Mendel and his contributions to the study of inheritance using these videos.

Resource Link

Resource Attribution
YouTube

Resource Type
Videos

Teaching Notes

These videos may be used as part of a flipped classroom model to introduce further activities that reinforce key concepts and vocabulary.

While much of this teaching box allows students to figure out the science behind genetics, it may be too much of a leap for students to be given Mendel’s pea plant data and come to the same conclusions as he did. This part of the unit may require some direct instruction, especially in regards to key vocabulary and the use of Punnett squares. These videos will need to be supplemented with other activities—there are many options available online and in traditional genetics units.

While few human traits follow the same inheritance patterns as those that were discovered by Mendel, he did discover some key features of inheritance that ring true for all traits (the concepts of segregation and independent assortment, that the alleles from each parent aren’t blended or altered in the offspring, and that all sexually reproducing organisms follow these same inheritance rules). While important for the discovery of other key concepts, dominance and recessiveness are often overemphasized in genetics units—I advise spending less time on them and providing more opportunities for students to investigate other patterns of inheritance.

Resource 5: A New Inherited Human Traits Survey

Students investigate human traits that are commonly introduced in biology classes as examples of monogenic inheritance patterns (two possible alleles: one dominant, one recessive). They analyze data about the inheritance patterns of each trait to determine which, if any, are truly monogenic in nature and would fit the inheritance patterns that Mendel observed in his pea plants.

Resource Link

Resource Attribution
Hilleary Osheroff, Exploratorium Teacher Institute
John McDonald, Myths of Human Genetics

Resource Type
Classroom Activity, Assessment

Teaching Notes

This is a continuation of the simple dominant/recessive inheritance patterns that Mendel discovered with his pea plant experiments and can be used as an assessment. Prior to this activity, students should be familiar with dominant and recessive alleles and their inheritance patterns. An understanding of Punnett squares may be useful as well.

The activity can be introduced the same way as a typical survey of human traits in a typical biology class: have students determine which combination of traits they have, then compare and contrast their combinations of traits with those of their classmates.

Discussion questions:

  • What do you notice?
  • If two people have the same combination of traits, what might that mean, if anything?
  • Notice that there were only two options for each trait—were there any traits where it was difficult for you to decide between the two options? Tell me why.
  • Do you think you can determine which traits are dominant and which traits are recessive?
  • Can you think of a better way to collect the data for some of these traits than just giving two options?

Divide students into groups of three or four and assign each group one trait to investigate. Give each group a copy of the data associated with their particular trait and have them make a claim—does it seem like this trait is inherited in the same way Mendel’s pea-plant traits were inherited, where one allele is dominant over another?

This is a good place to have students write a CER (claim-evidence-reasoning) to answer the question, Is this trait inherited the same way as the dominant and recessive patterns found in Mendel’s pea plant experiments?

Encourage students to explain their reasoning using Punnett squares.

The only two traits that may show indications of a similar dominant/recessive inheritance pattern are asparagus pee smell and earwax texture. The others, although presented as binary, are more complicated.

Debrief questions:

  • Which traits showed the same inheritance patterns as the pea plants?
  • What about the other traits? What do you notice?
  • What questions do you have about human inheritance after looking at the data?
  • Do all traits follow the same pattern of inheritance as Mendel’s pea plants? If not, what are other possible patterns of inheritance?

Resource 6: Mother & Child Reunion

Investigate other patterns of inheritance, including codominance, incomplete dominance, and multiple-allele traits, focusing on the genetics of blood type.

Resource Link

Resource Attribution
Daisy Yeung, Exploratorium Teacher Institute
Karen Kalumuck, Human Body Explorations: Hands-On Investigations of What Makes Us Tick

Resource Type
Classroom Activity

Teaching Notes

Most students are very interested in blood, blood transfusions, and blood types, and you may want to collect their questions before beginning this activity.

Prior to the investigation, you should introduce the inheritance of multiple-allele traits. This requires some direct instruction—see the PowerPoint linked to the Resource Link button above.

Because each “patient’s” blood is the same, but antibodies are different, I recommend creating stations for each patient so that the blood and antibodies stay together. It’s also important to stress to students to avoid cross-contamination, otherwise the results will be inaccurate.

After the investigation, it may be of interest to students to discuss blood transfusions and what blood type may be donated to which recipient.

Discussion questions:

  • What is different about the way blood type is inherited from the way pea plant traits are inherited?
  • What is the same?
  • What do you think these inherited “factors” actually are? What are they made of? How do they work?

Resource 7: DNA Structure Building Challenge

Investigate and build a model of the structure of DNA, the genetic material that’s passed from one generation to the next. Students can use historical data as pieces of evidence that accumulate over time, resulting in the discovery of DNA’s double helix structure.

Resource Link

Resource Attribution
Tammy Cook-Endres, Exploratorium Teacher Institute

Resource Type
Classroom Activity

Teaching Notes

Before this activity, you may want to do a DNA extraction lab to provide some context for students and to emphasize the importance of using models in science (the DNA you extract is visible with the naked eye, but the double helix is still too small to see).

This activity illustrates the nature of science and how scientific ideas change as evidence accumulates over time. It is helpful to show these changes by encouraging students to come up with multiple possible models with the initial clues, then eliminate possibilities as more evidence is presented.

Most students have seen a double helix before, so it is important to emphasize prior to this activity that, although the end result will be a double helix, they should base their models only on the evidence that is available.

Resource 8: Sizing Up—Genetics Version

Introduce students to the organization of genetic material (alleles, genes, chromosomes) and the relative sizes of molecules and cells involved in inheritance.

Resource Link

Resource Attribution
Karen Kalumuck & Tammy Cook-Endres, Exploratorium Teacher Institute

Resource Type
Classroom Activity

Teaching Notes

Students often struggle with finding a context for abstract concepts like DNA, genes, proteins, and cells that are too small to see (therefore, students often use these words interchangeably to mean the same thing, when they aren’t). This activity provides a more relatable image of how molecular structures compare.

This HHMI video may also help students visualize the molecules involved. It is important to emphasize that DNA and chromosomes are large, complex molecules that look different when viewed at different scales. This is especially important because different models are used to represent these molecules, which can be very confusing for students.

Discussion questions:

  • What have we figured out so far about DNA?
  • What questions do you still have?
    • Ideally, we want students to land on the question: We know that DNA is the molecule that’s passed from parent to offspring, but how does that happen? And how does that lead to genetic variation in families?

Resource 9: Meiosis Chromosome Pairing Activity

Simplify the complex structure of chromosomes to allow students to compare and contrast the differences between genes, alleles, and homologous chromosomes.

Resource Link

Resource Attribution
Daisy Yeung, Exploratorium Teacher Institute

Resource Type
Classroom Activity

Teaching Notes

Provide each student with a chromosome and ask them to find their match. Their initial instinct is often to find someone with an identical chromosome. They will come to realize that some colors don’t match up exactly (i.e., pink with red, orange with brown), but the sizes of the matching chromosomes and the locations and numbers of the alleles are the same. You can lead a discussion to address these noticings:

  • How did you find your match?
  • What was different about your match? What was the same?
  • Why do you think there are always two matching chromosomes? (For an additional challenge, you may incorporate X and Y chromosomes, in which case, you could ask if anyone couldn’t find a match)

This is a good place to define key terms like chromosome, homologous chromosome, gene, and allele.

Resource 10: Modeling Meiosis

Let students design a pathway to represent the steps of meiosis given the starting and ending cells in the process. They’ll repeat the process three times, each time with added complexity. Introduce students to segregation, independent assortment, and crossing over.

Resource Link

Resource Attribution
Hilleary Osheroff, Exploratorium Teacher Institute

Resource Type
Classroom Activity

Teaching Notes

You may choose to give students a more open-ended prompt or a more guided one for the first model, but challenge them to draw a model of at least two possible pathways.

  • If you want to provide more restrictions for their model, you may tell students that they may only do two things: duplicate chromosomes or split cells in half.
  • This first model can be used to help inform their subsequent models (one model may end up fitting better with the additional data to come, which is why it’s important that students draw out at least two options to start)

Provide the next model (2a) and have students repeat the same process. Then provide the next model, and finally the next. At some point, students will narrow down the order of operations to only one possibility to fit the data provided. At that point, you can introduce the three major concepts represented: segregation, independent assortment, and crossing over.

This would also be a good place to define key terms like gamete, haploid, and diploid.

This is also be a good time for students to revisit their initial models and add to or change them.

Discussion questions:

  • Compare the initial cells with the final cells in each round. How are they different? How are they the same?
  • Based on what you modeled in this activity, why do siblings not look identical even though they have the same biological parents?
  • Ideally, after this activity, students would land on a question that sounds like: Now we know why the DNA in siblings is never the same, but how does the information in DNA become a physically formed trait that we can see, like eye color or earwax texture?

Resource 11: Breakfast Proteins

Use a colored cereal bracelet built from a code as an analogy for the central dogma.

Resource Link

Resource Attribution
Exploratorium

Resource Type
Classroom Activity

Teaching Notes

This activity could be used as an initial shared experience for students to refer back to as they explore the central dogma, or it could be used as an assessment afterward to check for understanding.

Discussion questions (if using as initial phenomenon):

  • Describe the steps of the process for building your cereal bracelet.
  • How did you know how to build the correct cereal bracelet?

If using as a check for understanding, you may choose to use the graphic organizer linked above to help students clarify their thinking. Secret Codes could be used as an alternative introduction to reading the genetic code.

Resource 12: Protein Synthesis Simulation

Let students try a few ways of simulating the steps of protein synthesis (transcription and translation).

Resource Link

Resource Attribution
Exploratorium
Explore Biology
Woodside High School

Resource Type
Classroom Activity

Teaching Notes

Some direct instruction about transcription and translation is necessary before beginning these simulations. Here are some helpful web resources:

The simulations are arranged from simplest to most complex in terms of materials and setup. Use the one that’s most appropriate for the resources available to you.

It’s important for students to analyze the strengths and weaknesses of each simulation. Discussion questions:

  • In what ways was this simulation an accurate representation of the steps of protein synthesis?
  • In what ways was this simulation inaccurate?

Resource 13: Pencil Transferase

Investigate the connection between a protein’s structure and its function.

Resource Link

Resource Attribution
Jeanne Ting Chowning, The American Biology Teacher

Resource Type
Classroom Activity

Teaching Notes

It may be helpful to supplement this activity with other protein structure and function activities if proteins have not been discussed in detail in prior units of study. Resources for these additional activities are not provided here, but the following Web searches are a good place to start:

  • Lactase persistence
  • Catalase
  • Amylase

Discussion questions:

  • What is similar between your pencil transferase and your partner’s?
  • What is different?
  • Look around the room. Is there anything that everyone’s pencil transferases have in common?
  • If something were to go wrong with the shape of your pencil transferase (mutate), where would that mutation have the largest impact on your protein’s ability to function? Where would that mutation have less of an impact?

Resource 14: Mutate Your Name

Investigate the connection between a protein’s structure and its function.

Resource Link

Resource Attribution
Daisy Yeung, Exploratorium Teacher Institute

Resource Type
Classroom Activity

Teaching Notes

I allow my students to choose any name as long as it is 5–8 letters long. You have the option to add restrictions or have every student use the same name for the activity, although this takes a bit of the fun and personalization out of it.

It is useful to model each step with the class, especially the frameshift mutations.

Discussion questions:

  • In this model, if your name represents a protein, what do the letters of your name represent?
  • What would a change in the amino acid sequence look like on a real protein (how would a real protein be affected)?
  • Why is it possible for some mutations to not affect your name?
  • Which type of mutation do you think affects a protein’s structure and function more—substitution or insertion? Why?
  • How might mutations impact your initial model for explaining genetic variation among family members?

Resource 15: Modeling Gene Regulation

Simulate the genetic and environmental factors that affect skin color.

Resource Link

Resource Attribution
Hilleary Osheroff, Exploratorium Teacher Institute

Resource Type
Classroom Activity

Teaching Notes

This activity provides a concrete example of how a complex trait is controlled by multiple genes, hormones, proteins, and environment, but remember that this simulation is also extremely oversimplified.

The gene MC1R does not control skin color alone, but it does have a large impact. The effects of various alleles of MC1R on skin color are well-researched, and students’ predictions about what would happen to the system under various mutation scenarios of MC1R can be checked against real studies.

After this activity, it is important for students to revisit their initial models one more time and revise with new information. The revision in the middle of the unit may be skipped if needed, but this final revisit is critical for you to see any change in understanding.

Resource 16: Genetics Storyline Sequence

This is the guiding document used to organize this digital teaching box. The structure is based on the Next Generation Science Storylines from Northwestern University.

Resource Link

Resource Attribution
Daisy Yeung, Exploratorium Teacher Institute

Resource Type
Teaching guide

Teaching Notes

This resource is meant to show the scope and sequence of the unit. While the resources in this digital teaching box are presented in the same order as those in the storyline, this is only a suggested sequence. The order of activities really should depend on the questions your students want to investigate, to help them create a revised model for the anchoring phenomenon. Each activity or investigation should lead to questions that motivate the next activity or investigation in the sequence.

NGSS Alignment

Science and Engineering Practices

Asking Questions and Defining Problems 
Ask questions that arise from examining models or a theory to clarify relationships. (HS-LS3-1)

Analyzing and Interpreting Data 
Apply concepts of statistics and probability to scientific and engineering questions and problems, using digital tools when feasible. (HS-LS3-3)

Engaging in Argument from Evidence 
Make and defend a claim based on evidence about the natural world that reflects scientific knowledge, and student-generated evidence. (HS-LS3-2)


Disciplinary Core Ideas

LS1.A Structure and Function 
All cells contain genetic information in the form of DNA molecules. Genes are regions in the DNA that contain the instructions that code for the formation of proteins. (HS-LS3-1)

LS3.A Inheritance of Traits 
Each chromosome consists of a single very long DNA molecule, and each gene on the chromosome is a particular segment of that DNA. The instructions for forming species’ characteristics are carried in DNA. All cells in an organism have the same genetic content, but the genes used (expressed) by the cell may be regulated in different ways. Not all DNA codes for a protein; some segments of DNA are involved in regulatory or structural functions, and some have no as-yet known function. (HS-LS3-1)

LS3.B Variation of Traits

  • In sexual reproduction, chromosomes can sometimes swap sections during the process of meiosis (cell division), thereby creating new genetic combinations and thus more genetic variation. Although DNA replication is tightly regulated and remarkably accurate, errors do occur and result in mutations, which are also a source of genetic variation. Environmental factors can also cause mutations in genes, and viable mutations are inherited. (HS-LS3-2)
  • Environmental factors also affect expression of traits, and hence affect the probability of ocurrences of traits in a population. Thus the variation and distribution of traits observed depends on both genetic and environmental factors. (HS-LS3-2, HS-LS3-3)

Crosscutting Concepts

Cause and Effect 
Empirical evidence is required to differentiate between cause and correlation and make claims about specific causes and effects. (HS-LS3-1, HS-LS3-2)=

Scale, Proportion, and Quantity 
Algebraic thinking is used to examine scientific data and predict the effect of a change in one variable on another. (HS-LS3-3)

Science is a Human Endeavor (Connection to Nature of Science)

  • Technological advances have influenced the progress of science and science has influenced advances in technology (HS-LS3-3)
  • Science and engineering are influenced by society and society is influenced by science and engineering. (HS-LS3-3)