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Genetics for All

Supporting targeted populations in biology

Introductory genetics is traditionally a challenging topic because the concepts are abstract, and it includes a fair amount of discipline-specific vocabulary. As schools become increasingly diverse, science teachers must consider instructional strategies that provide equitable access for all students, namely supporting the language development that leads to rigorous science learning (Januszyk, Miller, and Lee 2016).

Lewis and Wood-Robinson (2000) found students had “limited understanding of the nature of genetic information,” and they expressed concern about the level of confusion regarding “basic biological structures (such as cell, chromosome, and genes) and their relationship to each other.” Kademian and colleagues (2017) reported the difficulties that science teachers encounter when using scientific language in the classroom. Thorne, Gericke, and Hagberg (2013) and Bahar, Johnstone, and Hansell (1999) also found that students experienced linguistic challenges when studying genetics. We expect these challenges to be more pronounced for students who are English language learners (ELLs), have individualized education programs (IEPs) for language processing disorders and reading comprehension, and have low Lexile reading scores.

Our context

This genetics unit was taught in a Title I urban high school in the southwestern United States. There were 36 ninth and 10th-grade students in the biology class. Although class-level demographics were not available, the biology classes are not tracked and all students take general biology. In the school, 13% of students are designated as ELLs, 15% have IEPs, and 64% are Hispanic/Latino, 22% are African American/black, and 7% are white. Additionally, 70% of students at this school are eligible for free and reduced-price lunch. The Lexile scores of the students in this classroom ranged from 575 to 1550, with an average Lexile score of 1001, corresponding to middle school reading levels (NGAC and CCSSO 2010).

This school operates on a block schedule, semester-based system with 10 hours of science class per week. Science teachers at this school site are expected to schedule opportunities for students to use Achieve3000, an intervention used to promote literacy (see “On the web”). In this particular classroom, there are two credentialed secondary science teachers who co-teach.

The teachers in this classroom begin each day with a quick writing prompt of one to three questions that the students answer on their own and then discuss. While students are working, the teachers circulate the room, look at students’ work, and have conversations with students to gauge understanding. These quick writes serve as the teachers’ primary form of formative assessment. Depending on the length of the quick write and the subsequent discussion, the time spent averages 20 minutes.

It is common in this classroom for activities to be conducted in stations. On days when stations are used, three 45-minute stations are organized, with 12 students at any one station at a time. Two stations are led by the teachers and the third station is an opportunity for students to complete their Achieve3000 literacy activities. Station work reduces the teacher-to-student ratio, allowing the teacher to work more closely with each student.

Of the activities presented here, the PTC Genetics Lab was completed during station work rotations. A student in this classroom approached one of the authors and explained that she, “really likes stations because it lets me get one-on-one attention from the teacher.” With increasing class sizes, we recognize that station work acts as an additional support to students by allowing each student to have closer interactions with their teacher.

Students transcribe and  translate a given sequence  while engaging in the How to Build a Car activity.

Students transcribe and translate a given sequence while engaging in the How to Build a Car activity.

Activity A: How to build a car

This activity was adapted from CPALMS’s “Protein Car Synthesis” (see “On the web”). Here, students learned about the processes of transcription and translation through a short story and hands-on activity using an analogy of building a car. The goals of this assignment were for students to enact the processes of transcription and translation for a short segment of DNA and to understand how a simple code can produce a complex structure.

Each student was given a copy of “How a Car (Protein) is Built (Synthesized)” (Figure 1) and a cell diagram that depicts where transcription and translation occur in the cell and the major organelles involved. As one teacher read the story aloud to the class, the other teacher assisted the students in making annotations on the cell diagram. This story discusses how RNA polymerase transcribes DNA into mRNA, which is used by the ribosome to create a protein.

FIGURE 1
How to build a car worksheet

How to build a car worksheet

Reading the story aloud supports all students in comprehending content, especially those with lower reading levels (Delo 2008). Additionally, the story connected academic language to more familiar language, making the academic vocabulary more accessible for ELLs. This support proved to be invaluable throughout the activity; the teacher noted students’ discussions transitioning from the production of cars to explaining the processes of transcription and translation.

After reading the story, students worked in groups of four or five to transcribe and translate a segment of DNA. The groups were given a short sequence of DNA and analysis questions (see “On the web”). From the DNA sequence, students had to make sense of patterns to create a protein (represented by a drawing of a car). The car could be built only if they successfully transcribed and translated the DNA sequence.

The codons were written on index cards, and each card had a section of a car printed on the back. When students turned the codons over, they could assemble a car from the cards. As students manipulated the codons on the index cards, the teachers asked questions, such as, “What is a codon?” “What are you trying to produce?” “What might happen to the car (or the protein) if the codon was changed?” and “How does the car represent a protein?” These scaffolded questions helped check for understanding and encouraged students to think more deeply about the content embedded in the activity.

Completing the analysis questions allowed the students to consider what would happen to their cars and to the gene that controls lactase if transcription was incorrect. In considering these questions, students thought critically about the structure and function of genes and made evaluations about transcription errors and communicated this in their science notebooks. This activity took approximately 90 minutes to complete. The quick write administered the day following this activity assessed their ability to simulate transcription and translation.

Activity B: PTC genetics lab

We adapted this laboratory experience from MiniOne’s “A Taste of Genetics MiniLab” (see “On the web”). Students used gel electrophoresis equipment to learn about genetics and genotyping, using the ability to taste phenylthiocarbamide (PTC) as the phenotype. The goals of this assignment were to recognize there is a gene that codes for a specific protein involved in taste receptor cells, to explain an example of how inheritance of traits leads to variation, and to read scientific literature and communicate technical information.

While completing the analysis questions for the How to Build a Car activity, students consider what would happen if transcription occurs incorrectly

While completing the analysis questions for the How to Build a Car activity, students consider what would happen if transcription occurs incorrectly.

Students completed the activity during a 45-minute-long station. The teacher asked one student to read the Background and Taste and Genetics sections from the PTC Genetics Lab handout (see “On the web”) to the group. The teacher supported the students when they reached challenging vocabulary and led the group in a brief discussion about these terms. Students, instructed to only taste clean PTC paper supplied by the teacher, then place a strip on their tongues to determine whether they could taste PTC. Students who tasted nothing were considered a non-PTC taster and students who tasted something bitter were considered a PTC taster. After each student determined their phenotype, the teacher led a discussion on how the classroom population differed for this trait.

The students continued reading a scenario about a student named Jill, who discovered that she was a non-PTC taster in her science class. In the scenario, Jill tested her whole family for the PTC-tasting trait. The students each then hypothesized why Jill cannot taste PTC and her entire family can.

The teacher provided a sentence starter to support the students in developing their own claim, “Jill can’t taste PTC while her parents can because….” Hill and Hoak (2015) emphasize that no one’s first language is academic language and supports must be provided to all students so they are on equal footing. Sentence starters are one strategy that Hill and Hoak (2015) suggest for supporting students’ learning to use academic language in the classroom. After writing their hypotheses, students shared their ideas with a partner and had time to revise prior to sharing with the whole group. The teacher asked students to elaborate on their claims, when needed.

Each student group, approximately 12 students, worked together on one gel. Before the class started, the teacher had prepared the gel and the gel electrophoresis box. The MiniOne’s lab kit came with samples for Jill, Jill’s mother, father, and two brothers pre-prepared and ready to be loaded into the gel.

Before beginning, the teacher explained to the students how to properly use a micropipette and demonstrated its use without the gel and also while loading the ladder into the gel. The teacher instructed each student to wear safety glasses and gloves while working around the gel. The teacher then monitored the students as they loaded the remaining samples into the gel, taking care to use a new pipette tip for each sample.

The gel electrophoresis procedure ran for about 20 minutes. The teacher explained what was happening inside the box, including how the size of the DNA fragments influenced how far the fragments travel down the gel. Each student looked at the gel under a UV lamp and drew a diagram of the gel in their notebooks. Students explored how traits vary between siblings and among other family members, using Punnett squares to understand the data and results. The students were given the opportunity to make sense of the genetic patterns of inheritance. As the students completed their analysis, the teacher walked around to see how each student was answering the questions, to question students further, and to support students in their sensemaking.

There are multiple opportunities for formative assessment during this activity: students’ understanding of genetics vocabulary, understanding of inheritance from their hypotheses, and understanding of inheritance from the answers to the analysis questions. The total time that this activity took was approximately 45 minutes. Following this activity, the quick write assessed the students’ ability to solve monohybrid genetic crosses.

Activity C: Biotechnology Socratic seminar

The Socratic seminar provided the opportunity to assess how students applied the claim-evidence-reasoning (CER) writing framework and honed their scientific communication skills. Working in groups of three, students prepared claims for three different biotechnology topics: cloning, genetic testing, and stem cell research. The goals of this assignment were to practice and demonstrate competency in using the CER framework, to search, read, and analyze scientific literature, and to engage in scientific argumentation.

Students prepared for the seminar with a graphic organizer (see “On the web”), which included sentence starters: “According to the article, “[BLANK]”, the author states…” and “According to an article on [BLANK] website … .” These sentence starters served as a support to use CER for ELLs in the classroom. The graphic organizer also included questions related to the three topics of the Socratic seminar:

  • Bulls, sheep, and pet dogs have been successfully cloned. At what point should we stop researching what can be cloned? Should we attempt to clone humans? Why or why not?
  • If given the opportunity, would you want to have genetic testing? Why or why not?
  • Should stem cell research be limited to only extinct species?

During the Socratic seminar, each member of the groups of three had a role: speaker, note-taker, and assessor. The students sat in two different circles. The speakers (one speaker per triad) made up the inner circle, while the note-taker and assessor sat behind the speaker in the outer circle. The speaker presented the group’s claim, evidence, and reasoning, and engaged in argumentation with their peers.

After round one (cloning) was complete, the students switched roles for the next topic (genetic testing), and switched again for stem cell research. This allowed for students to experience each role, in which all consumers of science should be able to engage. The students were able to choose the order they engaged in each role, making students feel more comfortable.

In preparation for the Socratic seminar, the teachers supported students using role play, where each role helped students visualize what the seminar should look like. We noticed that the students were more confident and excited to begin the Socratic seminar after watching the teachers’ example. During the seminar, students were provided with discussion sentence starters, “I believe …, I agree with your claim and …, that was a great point but … .” The use of sentence starters specifically supported the ELLs to engage in the discussion.

Because this was a multiday activity, multiple quick writes were administered. For example, one asked for students to evaluate an example of claim-evidence-reasoning, and provide reasons for their evaluations.

Conclusion

The assignments presented here are only a snapshot of what was completed over the course of this four-week unit. Due to course structure, a formal assessment was not administered for this unit, so we can only provide our observations on the engagement and inclusion of all students in the classroom. We noted nearly full participation in all three activities, particularly during the hands-on portions and during the discussions, and that these activities made genetics accessible to all students in this classroom. We hope readers of this article can use and adapt these activities to help support their students in learning about the abstract nature of genetics. By making science more accessible to all students, we are able to increase students’ engagement with science, and hope to spark their interest in becoming future scientists.

Lauren Stewart (lnstewart@sdsu.edu) is a doctoral student and Donna Ross is an associate professor at San Diego State University–Center for Research in Mathematics and Science Education. Kimberly Elliot is a biology teacher at Health Sciences High and Middle College, San Diego, California, and a doctoral student at San Diego State University.

Connecting to the Next Generation Science Standards

Standards

HS-LS1 Structure and Function

HS-LS3 Heredity: Inheritance and Variation of Traits

Performance Expectations

The chart below makes one set of connections between the instruction outlined in this article and the NGSS. Other valid connections are likely; however, space restrictions prevent us from listing all possibilities.

The materials, lessons, and activities outlined in the article are just one step toward reaching the performance expectations listed below.

HS-LS1-1. Construct an explanation based on evidence for how the structure of DNA determines the structure of proteins, which carry out the essential functions of life through systems of specialized cells.

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

DIMENSIONS

classroom connections

Science and Engineering Practice

 

Analyzing and Interpreting Data

Analyze data using tools, technologies, and/or models in order to make valid and reliable scientific claims. 

Apply concepts of statistics and probability to scientific and engineering questions and problems, using digital tools when feasible. 

Students use gel electrophoresis to determine the genetic makeup of individuals with a known phenotype. 

Students use Punnett squares to understand the prevalence of the PTC-taster and non-taster traits in a familial population.

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.

Students investigate unknown genotypes using gel electrophoresis. The sizes of the DNA fragments determine where on the gel the fragment ends, which is used to determine the genotypes of the individuals.

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. 

Students investigate how traits are inherited in a single-family unit. Namely, how children inherit traits from their parents.

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. 

Students explain how a child can display different traits (PTC non-taster) than both of the child’s parents (PTC tasters).

Crosscutting Concepts

 

Patterns

Students observe patterns in systems at different scales and cite patterns as empirical evidence for causality in supporting their explanations of phenomena. 

Students determine individuals’ genotypes based on patterns of DNA fragment number, size, and placement. 

Structure and Function

The functions and properties of natural and designed objects and systems can be inferred from their overall structure, the way their components are shaped and used, and the molecular substructures of its various materials. 

Students investigate how variation in the same gene results in different phenotypes (PTC taster and non-taster).

References

ON THE WEB

Achieve3000

CPALMS Protein Car Synthesis

A Taste of Genetics MiniLab

REFERENCES

Bahar M., Johnstone A.H., and Hansell M.H.. 1999. Revising learning difficulties in biology. Journal of Biological Education 33 (2): 84–86.

Delo L. 2008. Reading aloud. The Science Teacher 75 (5): 33–37.

Hill J.D., and Hoak K. 2015. Middle school academic talk: The key to ensuring access for all. Principal Leadership 15 (6): 44–47.

Januszyk R., Miller E.C., and Lee O. 2016. Addressing student diversity and equity. Science and Children 53 (8): 28.

Kademian S.M., Arias A.M., Davis E.A., and Sullivan Palincsar A. 2017. Supporting the use of scientific language: Teachers’ use of content-foregrounded educative features. Journal of Science Teacher Education 28 (2): 146–168.

Lewis J., and Wood-Robinson C. 2000. Genes, chromosomes, cell division and inheritance—do students see any relationship? International Journal of Science Education 22 (2): 177–195.

National Governors Association Center for Best Practices, Council of Chief State School Officers (NGAC and CCSSO). 2010. Common Core State Standards for English Language Arts. Washington DC: NGAC and CCSSO.

NGSS Lead States. 2013. Next Generation Science Standards: For states, by states. Washington, DC: National Academies Press. .

Thorne K., Gericke N.M., and Hagberg M. 2013. Linguistic challenges in Mendelian genetics: Teachers’ talk in action. Science Education 97 (5): 695–722.

Biology Disabilities English Language Learners Equity High School

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