DNA Family Relationship Analysis (Genetics)

Sharon Schleigh Victor Sampson
Type Category
Instructional Materials
Lesson/Lesson Plan
This resource, vetted by NSTA curators, is provided to teachers along with suggested modifications to make it more in line with the vision of the NGSS. While not considered to be "fully aligned," the resources and expert recommendations provide teachers with concrete examples and expert guidance using the EQuIP rubric to adapted existing resources. Read more here.



This is one of 30 lessons from the NSTA Press book Scientific Argumentation in Biology. The lesson engages students in an argumentation cycle in which they determine if an individual could be the abducted son who disappeared 20 years prior. The lesson engages students by posing the question of whether or not the individual could be a member of this family. The lesson begins by discussing background information of Short Tandem Repeats (STRs) of DNA segments as genetic markers. The students are then given diagrams of the STR Family Relationship Analysis Test from four different chromosomes and a diagram of the lab protocol for the setup for the analyses. The test analysis is for one parent, four potential siblings and the individual in question. Through analysis of the diagrams, students must then decide and present evidence as to whether or not the individual in question could be a family member. Students are challenged to collect evidence needed to construct an argument defending their claim of relationship. As they construct this argument, students build and apply knowledge of genetic markers and STRs. This lesson is intended for middle or high school students. The reading level of this activity is more suitable to secondary level or advanced middle school. Teachers are encouraged to refer to the preface, introduction, student assessment samples, and appendices provided in the full book for important background on the practice of argumentation and resources for classroom implementation.

Intended Audience

Educator and learner
Educational Level
  • High School
Access Restrictions

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Performance Expectations

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.

Clarification Statement: none

Assessment Boundary: Assessment does not include identification of specific cell or tissue types, whole body systems, specific protein structures and functions, or the biochemistry of protein synthesis.

This resource is explicitly designed to build towards this performance expectation.

Comments about Including the Performance Expectation
This collection of lessons was published before the final release of the NGSS. However, the lessons are explicitly aligned to Disciplinary Core Ideas, Crosscutting Concepts, and Science and Engineering Practices from the Framework for K-12 Science Education. In science and in the classroom, the practice of engaging in argument from evidence will often precede the development of a generally accepted explanation for a phenomenon. Throughout this lesson, students will develop and revise oral and written explanations that detail their understanding of STRs and genetic markers. Student will draw on evidence collected during their analysis of the STRs on specific chromosomes, but teachers may also present additional learning experiences prior to or within this lesson. Teachers will need to plan for an extension of this lesson or for an additional lesson to address that concept. The teacher notes provide some guidance on how this lesson can fit into various parts of a typical biology course. The preface, introduction, student assessment samples, and appendix of the full book provide the teacher with background on how to support students in their small group work and facilitate class discussions as they progress through the argumentation cycle.

Science and Engineering Practices

This resource is explicitly designed to build towards this science and engineering practice.

Comments about Including the Science and Engineering Practice
This lesson is centered around the practice of Engaging in Argument from Evidence and will engage students in many of the elements of that practice. In particular, this lesson calls on students to evaluate the possibility of relationship between the individual in question, one parent and four siblings. Correct analysis of each gel diagram is imperative and students may need assistance with their analyses. Constructing defensible arguments is the goal of this activity and the teacher will need to be prepared to support students in that phase of the lesson. The final goal of the lesson is for students to produce a written argument that includes an explanation of the relevant concepts of the location of STRs and the supported or refuted family relationships. The authors also suggest that the lesson addresses the practice of Developing and Using Models. While this practice is not addressed explicitly within the lesson, the lesson framework would certainly accommodate the development and revision of student models as the basis for their arguments and explanations. Students may, on their own, incorporate simple models into their arguments. However, teachers who wish to focus on modeling within this lesson will likely wish to make this connection more explicit as they facilitate the lesson with their students.

Disciplinary Core Ideas

This resource is explicitly designed to build towards this disciplinary core idea.

Comments about Including the Disciplinary Core Idea
Diagrams of four different chromosomes provide the heart of the information for students. The student handouts also contain diagrams of the protocol for making the gels that are used to develop the diagrams of each of the four chromosomes. If students are not familiar with this protocol, completing a lab utilizing this protocol or doing a simulation of this protocol provided on the internet would be helpful to students making the connections between extracted DNA, STRs and genetic markers. Students may also have some difficulty interpreting the provided DNA marker diagrams and utilization of simpler but similar diagrams found on multiple sites can help with this. The teacher notes do provide an accurate discussion of the concepts involved. Outside of the teacher notes, the lesson does not include direct instruction on the concepts of the Disciplinary Core Idea. Rather, the argumentation cycle provides a context in which students can apply their understanding of these concepts. Students may gain these understandings through prior instruction, instruction embedded within the argumentation cycle, or self-directed research within the argumentation cycle. The teacher notes describe the alignment between the lesson and the Disciplinary Core Ideas. The scenario provides an engaging context to which students can connect their learning about applications of genetics and DNA technology involving societal issues.

Crosscutting Concepts

This resource is explicitly designed to build towards this crosscutting concept.

Comments about Including the Crosscutting Concept
Focusing on the connections to the Cross Cutting concept of cause and effect relationships will maximize student learning in relation to the targeted Disciplinary Core Idea and Performance Expectation. Teachers should also consistently challenge students to use concepts of cause and effect as the students make claims based on their experimental data. Teachers should regularly ask students questions like, “What is your evidence for what you are claiming?” or “what is your evidence that makes this statement true?”

Resource Quality

  • Alignment to the Dimensions of the NGSS: This and the other lessons in this book were designed explicitly to address the three dimensions of the Framework for K-12 Science Education. Teachers are advised to familiarize themselves with Sampson and Schleigh's argumentation framework, suggested teacher behaviors, and assessment approaches before implementing this lesson in the classroom. The disciplinary core idea, the cross cutting concept and the practice addressed by this lesson all coherently work together to support students in three dimensional learning. The lesson centers on the phenomena of the family relationships being determined by genetic makeup of the individual. The lesson resources do not include instructional materials that directly present the core concepts targeted by the lesson. Rather, the teacher will need to provide such instruction prior to or embedded within the argumentation cycle.

  • Instructional Supports: The lesson begins with an explanation of short tandem repeats (STRs) and their connection to genetic markers. The location and size of STRs an individual has is dependent upon the DNA inherited from each parent. The students must be familiar with Mendelian inheritance and DNA structure as well as different modes of inheritance such as incomplete dominance, multiple alleles, and polygenic inheritance. The teacher might wish to enhance the lesson opening by incorporating a short formative assessment prompt to activate students’ prior knowledge of Mendelian genetics and/or DNA structure. The preface, introduction, assessment chapter, and appendix of the full book provide additional ideas for expanding and enhancing the lesson as well as supportive resources.

  • Monitoring Student Progress: Constant monitoring and feedback are built in to the Sampson and Schleigh's argumentation framework, but are reliant on skillful teacher interactions with students. Supportive questioning is critical to student success in this and similar lessons. Teachers should monitor and provide feedback to students as they construct initial arguments, present and critique arguments, and draft final written arguments. Teachers can also model and guide students in providing constructive peer feedback. Teachers should also consider allowing students to revise and improve final written arguments based on teacher and peer feedback.

  • Quality of Technological Interactivity: This is not a technology-based lesson. Technology may be incorporated in supporting instruction.