Subject Area Description:



GENES AND HEREDITY

9th and 10th Grade Biology

Unit of Instruction

Steve Schreiner

EDTEP 587

13 March 2003

Subject Area Description:

GENES AND HEREDITY is a five-week-long unit for Grade 9 and Grade 10 students enrolled in biology. Each week consists of three 50-minute periods and one 90-minute period, so the unit will span a total of fifteen 50-minute periods and five 90-minute periods. The unit will focus the essential question: How do genes and DNA control life? The major concepts it will cover are the structure and function of DNA; the processes of replication, transcription, and translation; pedigrees and Punnett squares; mutation and genetic disease; and genetic testing bioethics. Students enrolled in this biology course are well-motivated and likely to attend college (over 92% of the school’s graduates pursue post-secondary education). This is most students’ first high school science course. Many students will later enroll in AP science courses, including AP biology. Prior to this unit, students will have completed units focused on “science as a tool” and “organization of living systems,” in which students will have gained familiarity with the process by which scientists ask and answer questions, will have had an opportunity to develop and test hypotheses of their own, and will have learned about the organization of life, from ecosystems to intracellular environments.

The GENES AND HEREDITY unit will culminate in two formal assessments and many informal assessments scattered throughout instruction. The first formal assessment will be performance-based, requiring students to create a formal report detailing an inquiry project in which students expose bacteria to ultraviolet light. Reports will include diagrams and descriptions of ultraviolet light mutation mechanisms, ultimately presenting how a change in DNA sequence can lead to changes in growth patterns, and how different lengths of exposure to ultraviolet light affects bacterial growth.

The second formal assessment will serve as the unit’s culminating project: students will take the role of genetic counselors. Working in pairs, students will receive hypothetical information from a young married couple expecting their first child. The young wife’s brother has just been diagnosed with a serious genetic disease (exact type to be determined later), and the wife is worried she may be a carrier of the trait. The couple wants to know the probability of their child being affected by the disease. Students will receive descriptions and causes of several genetic diseases, hypothetical family histories, hypothetical copies of blood tests, and hypothetical gel-electrophoresis results. Students will be asked to create a pedigree of the family and determine the odds of the faulty gene being present in the fetus. Since the young couple have little understanding of the processes involved in heredity (they are meeting with genetic counselors only upon the recommendation of their family physician), students will be asked to provide, along with an analysis of the family’s genetic lineage, a written explanation of the involved genetic processes—why the gene affects only certain family members, how the gene is passed from generation to generation, the specific abnormality in the DNA sequence, and the molecular process (to the level of protein encoding) by which that abnormality causes disease—all in terms that the couple can understand. The goal is to provide the couple with enough information that they can determine the proper course of action. Students will be evaluated on the strength of their reasoning and accuracy of the descriptions they provide.

Essential Question:

The essential question for the GENES AND HEREDITY unit is: How do genes and DNA control life? Researchers at the forefront of science still debate answers to this question, so I certainly will not expect students to be able to come to a definitive conclusion, but the unit will serve as an introduction to the use of genes and heredity as a means for predicting and explaining the processes of life. To begin answering this essential question, students must begin by understanding the structure and function of DNA. Students will need to understand the process by which DNA sequences change over time or via environmental effects, how those changes affect organisms, and how genetic material is transmitted to offspring. Since science is a predictive tool, students will need to learn how to predict inheritance patterns and frequencies using pedigrees and Punnett squares. Additionally, students need to learn how to use tools of biotechnology, such as gel-electrophoresis apparatuses and micropipettes, as well as inquiry skills, as methods of creating data that may provide possible answers about the role of genes and DNA in life.

Learning Goals and Related Objectives:

Goal 1: Students will learn that DNA molecules are long chains linking just four kinds of smaller molecules, whose precise sequence encodes genetic information. (EALR 1.2, Benchmark 3—Molecular basis of heredity: describe how genetic information [DNA] in the cell is controlled at the molecular level and provides genetic continuity between generations).

Objective 1.1: Students will understand that DNA is a double-helical molecule whose four different nucleotides encode genetic information.

Objective 1.2: Students will understand the process by which specific DNA sequences lead to specific proteins.

Objective 1.3: Students will construct a model of the DNA molecule and learn the names and functions of its parts.

Objective 1.4: Students will analyze DNA sequences to determine the amino acid sequences they encode.

Objective 1.5: Students will predict the effects of different mutations in the DNA sequence.

Goal 2: Students will learn that heritable characteristics can be observed at molecular and whole-organism levels—in structure, chemistry, or behavior. (EALR 1.2, Benchmark 3—Structure and organization of living systems: understand that specific genes regulate the functions performed by structures within the cells of multicellular organisms).

Objective 2.1: Students will understand that genes, encoded by specific DNA sequences, result in specific biological structures and behaviors.

Objective 2.2: Students will understand that Punnett squares and pedigrees are models used to predict and demonstrate genetic inheritance.

Objective 2.3: Students will determine whether various DNA samples carry the gene for sickle-cell anemia.

Objective 2.4: Students will construct pedigrees and Punnett squares that model genetic transmission among populations/families.

Goal 3: Students will learn that faulty genes can cause body parts or systems to work poorly and that some genetic diseases appear only when an individual has inherited a faulty gene from both parents.

Objective 3.1: Students will understand that specific changes in DNA sequences can lead to specific genetic deficiencies and diseases.

Objective 3.2: Students will understand the concepts of dominance, recessiveness, and co-dominance, as well as sex-linked and autosomal traits.

Objective 3.3: Students will use Punnett squares to predict the frequencies of genetic disease among disease-susceptible families.

Objective 3.4: Students will interpret data to develop hypotheses about whether certain genetic diseases are sex-linked or autosomal, and dominant or recessive.

Objective 3.5: Students will apply their knowledge of DNA structure to determine how faulty genes express abnormal proteins.

Goal 4: Students will begin to discover the interplay between science and ethics.

Objective 4.1: Students will understand that individuals decide whether to use advances in science and technology by addressing the ethical implications of those advances.

Objective 4.2: Students will apply a model for ethical decision-making to a genetic testing dilemma.

Goal 5: Students will design an investigation researching the effects of exposing bacterial colonies to varying amounts of ultraviolet light. (EALR 2.1, Benchmark 3—Designing and conducting investigations: design, conduct, and evaluate systematic and complex scientific investigations, using appropriate technology, multiple measures, and safe approaches).

Objective 5.1: Students will understand that exposure to ultraviolet light causes changes in the growth of bacteria.

Objective 5.1: Students will develop and test a hypothesis addressing exposure of bacteria to varying amounts of ultraviolet light.

Objective 5.2: Students will model the process by which ultraviolet light causes changes in bacterial growth.

DAY 1: Eliciting Student Responses (50 minutes) -- Monday

|What students are doing: |Students will engage in an introductory dialogue about genes, DNA, and genetic technologies that reflects|

| |current knowledge and interests of students. |

|Objectives: |Students will understand that DNA is the basic unit of heredity. Students will develop personal interest|

| |in the topic of genes and heredity and identify why knowledge of the topic is important for adult life. |

|Reasons for content and |Before beginning a unit on genes and heredity, it’s important that students achieve a basic understanding|

|instructional strategy: |of the reasons for learning about the topic. Students need a broad picture of the role of genes and |

| |heredity in modern society—talking about DNA without providing context would quickly diminish student |

| |interest. Providing students a chance to voice their knowledge and interests not only gives them |

| |practice “talking science” with others, but also allows me, as an instructor, to determine appropriate |

| |starting points for later discussion of the unit materials and identify the knowledge and |

| |misunderstandings students are bringing to the unit. |

|Evidence of |Students will verbally express their current knowledge of the topic; this will serve as a baseline for |

|understanding: |further instruction |

|Resources: |Photograph of Dolly the sheep, photograph of chromosomes, photograph of DNA model, photograph of |

| |cancerous tumor, photograph of chimpanzee, photograph of antibacterial soap. |

DAY 2: A Mysterious Case (50 minutes) -- Tuesday

|What students are doing: |Students will read a historical physician’s report describing a patient with unusual symptoms (now |

| |identified as characteristic of sickle-cell anemia, though students won’t know this until the end of |

| |class). Students will also read a family history of the patient, and will observe a sample of the |

| |patient’s blood under a microscope, comparing this sample with a normal blood sample. Upon completion of|

| |the day’s assessment activity (described in the “evidence” section), students will receive handouts |

| |describing the sickle-cell disease—its effects, its inheritance mechanisms, and its testing procedures |

| |with gel electrophoresis. |

|Objectives: |Students will understand the historical context for, and characteristics of, the sickle-cell disease. |

| |Students will develop a knowledge base for performing an experiment to detect the presence of the sickle |

| |cell gene. Students will develop hypotheses from given data. |

|Reasons for content and |A real-life genetic disease provides students an authentic interface for beginning their learning about |

|instructional strategy: |the role of genes and heredity in life. By synthesizing authentic written descriptions and physical |

| |observations of the sickle-cell symptoms, students will gain a stronger understanding of the sickle-cell |

| |disease than they would have gained through lectures or videos. They will actually take the role of a |

| |medical practitioner, trying to figure out the cause of the symptoms they see, based upon their current |

| |understanding of science. By taking an active role in an authentic medical activity, students will be |

| |more likely to understand the facts and symptoms of sickle-cell, both now and later in the unit. |

|Evidence of |Students will write hypotheses that account for the patient’s symptoms, integrating observations of blood|

|understanding: |samples with information from physician reports and family history. I will provide written feedback on |

| |their hypotheses. Later, as evidence of reading comprehension, students will (before reading sickle-cell|

| |information) write whether they agree or disagree with 5-10 statements about DNA/genes, such as “DNA can |

| |be extracted from any cell in the human body.” After reading the sickle-cell information, students will |

| |write whether they now agree or disagree with the statement—demonstrating how their knowledge changed. |

|Resources: |Description of patient presenting symptoms of sickle-cell anemia, family history of patient, microscopes,|

| |slide with normal blood, slide with sickle-cell blood, information on sickle-cell disease, inheritance, |

| |and testing via gel electrophoresis. |

DAY 3: Preparing to Test for the Sickle-cell Gene with Gel Electrophoresis

(90 minutes) – Wednesday/Thursday

|What students are doing: |Students will listen to brief direct instruction discussing restriction enzymes and gel electrophoresis. |

| |Students will learn to use micropipettes, and they will load wells in a gel-electrophoresis apparatus, |

| |knowing they’ll be asked to do the same thing, with real DNA samples, the following day. Upon completion|

| |of this activity, students will scan (mentally, not physically) a normal DNA sequence and a sickle-cell |

| |sequence with a restriction enzyme to determine where the enzyme will cleave each sequence. Students |

| |will predict the position of various samples in the gel after running the electrophoresis. |

|Objectives: |Students will understand the process by which a gel-electrophoresis separates DNA fragments. Students |

| |will learn the function of restriction enzymes and their use during gel-electrophoresis. Students will |

| |learn to use micropipettes to load DNA into wells. Students will predict the position of various samples|

| |in the gel after running the electrophoresis. |

|Reasons for content and |This day’s activities build on the prior day’s discovery of the sickle-cell disease, providing a further |

|instructional strategy: |opportunity for students to identify the role of genes and heredity in life. The day provides an |

| |opportunity for students to actually use biotechnology to develop knowledge. A lecture fits into my |

| |instruction here because I believe I can better explain, and make more personally relevant, information |

| |about the topic than can a textbook or handout. Additionally, this direct instruction provides me an |

| |opportunity to instantaneously determine whether students comprehend the information I am |

| |presenting—something I couldn’t do with a textbook. Later in the day, students will actually do the work|

| |of a restriction enzyme, rather than read about what a restriction enzyme does, and likely will gain a |

| |deeper and longer-lasting understanding of these enzymes, and the structure of DNA, by actively |

| |performing their functions. Lastly, asking students to predict the results of the gel-electrophoresis |

| |gives them practice developing scientific hypotheses. |

|Evidence of |Students will use a model for understanding restriction enzymes, working in pairs to complete a worksheet|

|understanding: |that asks students to find certain patterns in DNA sequences and cut the sequence at those points. |

| |Students will predict the results of the gel-electrophoresis for normal, carrier, and sickle-cell DNA |

| |samples. We will discuss results together as a class. |

|Resources: |Gel-boxes, micropipettes, fake DNA samples, model of restriction enzyme for demonstration, restriction |

| |enzyme worksheet. |

DAY 4: Running a Gel for Sickle-cell (50 minutes) – Friday

|What students are doing: |Students will perform the gel-electrophoresis procedure on known and unknown samples of DNA, to determine|

| |the genotype of the unknown samples (whether the unknowns are normal, carrier, or sickle-cell). |

|Objectives: |Students will understand the process by which a gel-electrophoresis separates DNA fragments. Students |

| |will test and analyze their hypotheses about the position of various samples of DNA. Students will |

| |determine whether unknown DNA samples carry the gene for sickle-cell anemia. |

|Reasons for content and |As yesterday, this day’s activities build on the prior day’s discovery of the sickle-cell disease, |

|instructional strategy: |providing a further opportunity for students to identify the role of genes and heredity in life. |

| |Further, the day provides an opportunity for students to actually use biotechnology to develop knowledge.|

| |“Doing” science is the hallmark of the effective science class, and this day will provide students with a|

| |chance to actually “do” the same science that has become common in professional science labs worldwide. |

| |This day’s lab activities will solidify student knowledge of scientific tools and vocabulary, |

| |specifically micropipettes and gel-electrophoresis boxes, since students will actually be using these |

| |tools. As students will be using and analyzing their hypotheses in a real-world setting, they will gain |

| |further experience developing scientific hypotheses. Additionally, students will achieve better |

| |understanding of the possibility of mutations in DNA structure by analyzing the specific mutation that |

| |leads to the sickle-cell disease in terms of a real-world laboratory activity, rather than a |

| |pen-and-paper worksheet. |

|Evidence of |Students will record results in their lab notebooks, and after completing the lab, they will analyze |

|understanding: |their hypothesis to determine whether the data fit their predictions. They will also analyze any |

| |possible sources of error. Additionally, students will be asked to describe how the specific mutation in|

| |the sickle-cell gene sequence results in different results during the gel-electrophoresis procedure. Lab|

| |notebooks will be collected Monday and written feedback about student thinking will be provided. |

|Resources: |Gel-boxes, micropipettes, control DNA samples, unknown DNA samples. |

DAY 5: Introduction to Bioethics (50 minutes) – Monday

|What students are doing: |Students respond to a variety of ethical dilemmas, beginning with a man who steals bread to feed his |

| |hungry family and progressing to bioethically-related dilemmas, such as whether human cloning is |

| |acceptable. Students are exposed to recent advances in biotechnology—intra-uterine prenatal surgery, |

| |cosmetic surgery, genetic testing, surrogacy, organ cloning, etc. Students determine the ideas and |

| |concepts important to making a bioethical decision. Students listen to brief direct instruction about |

| |the difference between science and ethics. Students hear that during the next few days, they’ll be asked|

| |to take the role of a member of a hypothetical family that is at-risk for Huntington’s disease, and that |

| |they’ll need to make a decision about the proper course of action. Students read a packet describing |

| |Huntington’s disease and the members of a susceptible family, each of whom is trying to decide whether to|

| |be tested for Huntington’s. |

|Objectives: |Students will understand that individuals decide whether to use advances in science and technology by |

| |addressing the ethical implications of those advances. |

|Reasons for content and |It’s very important to me that students take a personal interest in genes and DNA—I want them to |

|instructional strategy: |understand how these “invisible” concepts relate to daily life. I believe that by presenting students |

| |with a real-world (though hypothetical) ethical dilemma hinging on genetic technology, students will |

| |better understand the purpose of learning about genes and DNA. This day’s instruction begins by |

| |eliciting student responses, both to help students begin talking about personal decisions and as a way of|

| |helping students feel like they have a stake in instruction. |

|Evidence of |Students will read the Huntington’s disease background information and write five brief statements about |

|understanding: |the disease. Students will read the Huntington’s disease case and will create a family tree of the Klein|

| |family (they will later use this family tree to construct a pedigree, during a later lesson introducing |

| |pedigrees). I will evaluate the structure of this tree to ensure that students understand the family |

| |structure in the scenario. |

|Resources: |Photos of biotechnological procedures, handout describing Huntington’s disease, handout describing family|

| |case study. |

DAY 6: Using a Model for Ethical Decision-Making (50 minutes) -- Tuesday

|What students are doing: |Students use a model to discuss, in groups, appropriate solutions to an ethical dilemma involving |

| |prenatal testing for Down’s syndrome. This provides students with practice using the model before they |

| |use it to make decisions about Huntington’s disease. Students present their group’s decision to the |

| |entire class. Students watch a video presenting a Wenatchee family with Huntington’s disease, which |

| |interviews family members and shows the disease’s terrible effects. Students draw names from a beaker to|

| |discover which of the Klein family members they will represent the following day. |

|Objectives: |Students will understand that Huntington’s disease is a fatal, untreatable disease inherited by children |

| |from affected parents. Students will apply a model for ethical decision-making to a genetic testing |

| |dilemma. |

|Reasons for content and |Students may have felt overwhelmed trying to determine the proper course of action for the dilemmas |

|instructional strategy: |presented yesterday; today’s instruction provides students with a tool for thinking about ethical |

| |questions. By working in groups to develop solutions, students get a chance to talk with each other |

| |about personal values and ethical principles. The video presenting Huntington’s makes the disease more |

| |tangible. By creating short stories about their character, students will take a personal stake in the |

| |decision the make tomorrow. |

|Evidence of |Students write brief fictional stories describing the character they’ve drawn—providing the character’s |

|understanding: |history, interests, and values. |

|Resources: |Video on Huntington’s, copies of model for ethical decision-making, names of family members in beaker. |

DAY 7: Making a Real-Life Ethical Decision and Experiencing the Consequences

(90 minutes) – Wednesday/Thursday

|What students are doing: |Students are told they’ll be making a real-life ethical decision today. Each student will have an |

| |opportunity to receive test results for their character, assuming they want to receive them, and with the|

| |condition that they read and sign a genetic testing consent form. Students use the ethical |

| |decision-making model to decide whether their character should be tested for Huntington’s. Students work|

| |in groups, with other students representing the same character, to develop posters listing four reasons |

| |to test, four reasons not to test, and each student’s personal decision at the bottom. Students present |

| |these posters to their classmates, who list ideas they agree with and ideas they disagree with. Students|

| |receive test-consent forms and make their final decision. Students deciding in favor of the test receive|

| |results. Students reflect on their decision and how they felt discussing ethical issues with their |

| |classmates. |

|Objectives: |Students will apply a model for ethical decision-making to a real-life genetic testing dilemma. |

|Reasons for content and |Ethics could be a very intangible topic for students; today’s activity allows students to experience the |

|instructional strategy: |meaning behind ethical decisions. This class serves as a summary for the bioethics mini-unit, |

| |integrating students’ knowledge of Huntington’s disease with personal values and use of a model for |

| |ethical decision-making by requiring students to make a real-world decision. |

|Evidence of |Students write a reflection on their testing decision, noting how their beliefs changed and how they used|

|understanding: |the model to help them arrive at an appropriate solution. |

|Resources: |Test-consent forms, sealed test results for each character in the family. |

DAY 8: Pedigrees (50 minutes) -- Friday

|What students are doing: |Students will be presented with the concept of pedigrees as models of genetic inheritance. Students will|

| |develop several simple pedigrees, based on family descriptions presented on the overhead. When |

| |comfortable with the basic idea of pedigrees, students will develop progressively-complicated pedigrees. |

|Objectives: |Students will understand that faulty genes can lead to genetic disease. Students will learn to use |

| |pedigrees as models of genetic inheritance. |

|Reasons for content and |Now that students have a basic knowledge of the effects of faulty genes on humans (through their |

|instructional strategy: |experiences with sickle-cell anemia and Huntington’s disease), they are ready to describe disease using a|

| |scientific model. Introducing pedigrees before giving students direct experience with inheritance might |

| |have made the concept more difficult to understand. By asking students to actually create models based |

| |on provided family descriptions, rather than just read about pedigrees or examine existing pedigrees, I |

| |am giving them practice applying a scientific model. |

|Evidence of |Students will create a pedigree for the Klein family, based on the family tree they created earlier. |

|understanding: | |

|Resources: |Descriptions of various families on transparencies. |

DAY 9: Punnett Squares as Models for Inheritance (50 minutes) -- Monday

|What students are doing: |Students will compare their physical features with those of their classmates—for example, eye color, ear |

| |lobe shape, tongue rolling, and ability to taste test-strips. Students will listen to brief direct |

| |instruction regarding the use of Punnett squares as a tool for determining gene inheritance frequencies. |

| |Students will use Punnett squares to predict frequencies of various pairings. Additionally, students |

| |will listen to an introduction to the concepts of dominance, recessiveness, and co-dominance |

|Objectives: |Students will learn that Punnett squares are a model for predicting genetic inheritance frequencies. |

| |Students will understand the concepts of dominance, recessiveness, and co-dominance, as well as |

| |sex-linked and autosomal traits. Students will use Punnett squares to predict the frequencies of genetic|

| |disease among disease-susceptible families and determine whether certain traits are dominant, recessive, |

| |co-dominant, sex-linked, and/or autosomal. |

|Reasons for content and |Introducing Punnett squares at this point in the unit allows students to build on their knowledge of |

|instructional strategy: |genetics gained through their experience with sickle-cell anemia, Huntington’s disease, and pedigrees. |

| |Rather than just detect the presence of certain genes via biotechnology, students will now be able to |

| |predict the odds of their presence using a scientific model. Through use of Punnett squares as models |

| |for students’ personal genetic characteristics (such as ear lobe shape and eye color), I am making |

| |genetics more personally relevant, as students are investigating their own bodies rather than imaginary |

| |characters in a textbook. |

|Evidence of |Students will, in groups, create Punnett squares for various genetic pairings, beginning with features |

|understanding: |previously observed among classmates, and progressing towards pairings for individuals possessing genes |

| |for certain genetic diseases (including sickle-cell). Students will use Punnett squares and pedigrees to|

| |determine whether certain traits are dominant, recessive, co-dominant, sex-linked, and/or autosomal. I |

| |will collect student work and check for comprehension of the concept, providing feedback to students. |

|Resources: |Taste test-strips, handouts with Punnett squares. |

DAY 10: Structure of DNA (50 minutes) -- Tuesday

|What students are doing: |Students will begin by working in groups to create a large model of DNA out of paper. Students will be |

| |given patterns representing different portions of the DNA strand, which they will cut out and attach to |

| |each other to create the DNA molecule. Once students have completed constructing the model, they will |

| |listen to direct instruction discussing the names and function of the different structures they have cut |

| |and attached. |

|Objectives: |Students will construct a model of the DNA molecule and learn the names and functions of its parts. |

|Reasons for content and |Every biology textbook diagrams the structure of DNA, but these diagrams often seem a poor representation|

|instructional strategy: |of the actual DNA molecule. I believe that by helping students create their own physical model of DNA, |

| |they will be more likely to remember its structure. Additionally, as students will be active during its |

| |creation, and will actually “see and feel” the model they create, they may find DNA to be as real as a |

| |grizzly bear or butterfly, rather than an insignificant and invisible molecule. I have decided to use a |

| |lecture to describe the names and function of the different pieces of the DNA molecule because I can |

| |better structure students’ learning than could a textbook, whose diagrams and descriptions may appear |

| |immediately overwhelming with their vast unfamiliar vocabularies. I introduce the structure of DNA at |

| |this point because it has become necessary for further understanding of genes and heredity. |

|Evidence of |Students will draw and label the structure of DNA on a blank sheet of paper, writing the function of the |

|understanding: |various subunits of the molecule. |

|Resources: |Scissors, staplers, sheets of paper with patterns of DNA subunits, handout presenting how the subunits |

| |fit together. |

DAY 11: The Central Dogma—Transcription and Translation (90 minutes) – Wednesday/Thursday

|What students are doing: |Students will begin by deciphering a code (composed of only the letters AUGC) with a key that calls for a|

| |certain color for a certain sequence of letters. For example, the sequence AGC would code for yellow; |

| |AGG would code for blue. Students will create a band of color, with colored pencils or crayons, using |

| |the sequence of letters they have been provided. Upon completion of this task, students will listen to |

| |direct instruction introducing the topic of codons, amino acids, and proteins. Students will perform the|

| |same task as before, but this time instead of encoding colors, each sequence will encode specific amino |

| |acids. Students will be provided with a sheet that lists a letter corresponding to a specific protein |

| |sequence (i.e. ala-arg-gua-cys-tyr equates to the letter G). When converted from protein sequence to |

| |letters, these letters will spell a word, like the school mascot or something equally cheesy. |

|Objectives: |Students will learn the terms codon, amino acid, and protein. Students will understand the process by |

| |which nucleotide sequences encode genetic information. Students will analyze DNA sequences to determine |

| |the amino acid sequences they encode. |

|Reasons for content and |The Central Dogma is perhaps the most important concept in modern biology (only evolution might be more |

|instructional strategy: |important), yet few students understand it,—I think because they never get to actually “experience” the |

| |central dogma. Rather than read about translation, I want students to experience translation, so I have |

| |designed activities that will require students to actually perform the processes of translation. These |

| |activities, which scaffold students’ understanding to ultimately achieve a detailed and accurate |

| |comprehension of translation, will make translation accessible and interesting, and will further develop |

| |students’ knowledge of the structure of DNA, once we discuss how DNA is transcribed into RNA, during the |

| |second part of the lesson. Additionally, by first learning the functions of codons, amino acids, and |

| |proteins, before learning the names of these important structures, I believe students will be more likely|

| |to add these terms to their scientific vocabulary. |

|Evidence of |Students will demonstrate their understanding of translation by discovering the encoded word. Students |

|understanding: |will use the same RNA sequence they used to discover the encoded word, but this time will determine the |

| |DNA sequence that encoded that RNA strand. Students will then determine the specific amino acid sequence|

| |encoded by a specific DNA strand (first converting the DNA to RNA, then RNA to amino acids). Students |

| |who do not discover the encoded word will be encouraged to see me for further help. |

|Resources: |Colored pencils or crayons, handout listing various single-stranded DNA sequences, legend/key for |

| |converting code to colors, legend/key for converting code to amino acids. |

DAY 12: Replication (50 minutes) -- Friday

|What students are doing: |Students will discuss how a single fertilized egg can grow into an entire human organism, and will |

| |discuss the process by which clones are created. This discussion will lead to students recognizing the |

| |need for replication of genetic material within organisms. Students will listen to direct instruction |

| |discussing the process by which DNA sequences are replicated. Students will “unzip” a DNA molecule and |

| |create a complimentary strand for each side. They will then repeat the process, again doubling the |

| |number of DNA molecules present. |

|Objectives: |Students will determine the complimentary nucleotide sequence for a given sequence of DNA. Students will|

| |explain the process by which DNA is replicated. Students will analyze DNA sequences to determine the |

| |amino acid sequences they encode (this objective met via assessment activity). |

|Reasons for content and |Just as with transcription and translation, I believe students need to actively perform the process of |

|instructional strategy: |replication if they are going to gain a solid understanding of the concept. By replicating a single |

| |piece of DNA into several identical pieces, students will learn about replication—the final fundamental |

| |aspect of DNA structure and function. Additionally, by seeing how replication fits into the processes of|

| |transcription and translation, students will be more likely to integrate replication into their cognitive|

| |schema for DNA function. This day’s assessment activity not only demonstrates to students that |

| |complimentary strands encode identical information, but also provides me with information about how well |

| |students have understood recent topics of classroom instruction. |

|Evidence of |Students will be given a single-strand sequence of DNA and will be asked to write the complimentary |

|understanding: |sequence for that strand, translate that complimentary sequence into RNA, and then determine the amino |

| |acid sequence encoded by that RNA sequence. Students will also need to translate and transcribe the |

| |original sequence, and explain in words and/or pictures the process by which DNA is replicated. |

|Resources: |Handout listing several single-stranded and double-stranded DNA sequences. |

DAY 13: Mutation (50 minutes) -- Monday

|What students are doing: |This day’s instruction begins by returning to the mutation present in the sickle-cell gene. Students |

| |will analyze the mutation in terms of the Central Dogma, first replicating the mutant strand, then |

| |translating the mutant strand into RNA, and finally determining the amino acid sequence encoded by the |

| |RNA. They will compare this amino acid sequence to the sequence encoded by the normal (non-sickle-cell) |

| |gene. Upon successful completion of this activity, students will listen to direct instruction on the |

| |three types of DNA sequence mutations (nonsense, missense, and frame shift) and how these mutations |

| |affect amino acid sequence. Real-life examples of each type of mutation will be provided, and students |

| |will hear how mutations arise in the DNA sequence. |

|Objectives: |Students will understand that mutations occur naturally over time and via environmental conditions. |

| |Students will predict the effects of different mutations in the DNA sequence. |

|Reasons for content and |Students will best understand the different types of mutation by actually examining the changes each |

|instructional strategy: |mutation causes in amino acid sequence. This will provide students with knowledge of how mutations can |

| |lead to disease. Additionally, linking mutations in DNA sequence with real-life genetic diseases will |

| |help solidify students’ understanding of DNA sequence and function and may provide context for the |

| |micro-scale topics of instruction of the past week. |

|Evidence of |Students will be provided with a worksheet listing several “normal” and “mutant” DNA sequences, and |

|understanding: |students will determine whether each mutation is a nonsense, missense, or frame shift mutation, depending|

| |on the differences between the normal and mutant amino acid sequence (students will determine the amino |

| |acid sequences encoded by the given DNA strands and compare these sequences to determine the type of |

| |mutation). |

|Resources: |Handout providing various single-stranded and double-stranded DNA sequences, as well as mutant sequences.|

DAY 14: Inquiry Investigation – Building a Knowledge Base to Prepare for Inquiry (50 minutes) -- Tuesday

|What students are doing: |Students will conduct a short inquiry project on the effects of ultraviolet light exposure on bacteria as|

| |a function of time. Based on knowledge of mutation discussed during the previous class period, as well |

| |as knowledge of the specific mutation caused by UV light exposure (which will be gained during this class|

| |period), students will predict, test, and analyze the effects on bacteria colonies of various times of |

| |exposure to ultraviolet light. The inquiry project will conclude with a formal lab report detailing |

| |students’ hypotheses, procedures, and findings. |

| | |

| |The inquiry project will begin with a demonstration of the effects of UV light exposure on bacteria. |

| |Students will listen to brief direct instruction about the use of ultraviolet light as a drinking water |

| |sterilizer during backcountry camping, and will then view several normal plates of bacteria and several |

| |plates that have been exposed to UV light. Working in groups of four, students will write observations |

| |for each plate. Students will then use specific classroom resources, either textbooks or handouts (which|

| |will be provided), to discover the mechanism of mutation. These resources will only provide the specific|

| |mutation occurring in the DNA sequence; they will not discuss how the mutation causes changes in growth. |

|Objectives: |Students will understand that exposure to ultraviolet light causes changes in the growth of bacteria. |

| |Students will understand the mechanism of mutation by which ultraviolet light prevents bacterial growth. |

|Reasons for content and |Inquiry enables students to engage in the most authentic of scientific activities—experimentation. |

|instructional strategy: |Students will perform an inquiry investigation using ultraviolet light and bacteria because a complete |

| |understanding of the mechanism of mutation due to UV exposure integrates knowledge gained throughout this|

| |unit. Additionally, bacteria grow quickly, so the results of student experimentation can be quickly and |

| |easily observed. During this first stage of the inquiry process, I am providing students with an |

| |opportunity to observe mutant bacteria and discover for themselves, using skills gained over the past |

| |several days, how UV light affects bacterial growth. I am also providing real-world context to the |

| |investigation by presenting the use of UV light as a sterilization tool for drinking water. |

|Evidence of |Students will apply their knowledge of transcription and translation to determine the amino acid sequence|

|understanding: |encoded by normal bacterial DNA and the amino acid sequence encoded by mutated DNA. They will present |

| |and discuss their findings with their group the following day. |

|Resources: |Photo of UV water sterilizer, resources describing UV light mechanism of mutation, normal bacteria |

| |plates, UV-exposed bacteria plates, incubator, ultraviolet lamp box. |

DAY 15: Inquiry Investigation – Crafting Questions, Hypotheses, Predictions; and Designing the Investigation (90 minutes) – Wednesday/Thursday

|What students are doing: |Students will discuss, in the same groups of four, the amino acid sequences encoded by normal and mutant |

| |bacterial DNA strands to ensure that each group member understands the mechanism of mutation. Students |

| |will create a poster demonstrating this mutation mechanism. Students will be told their task is to |

| |predict the effects, on bacterial growth, of different times of exposure to UV light. In groups, |

| |students will design an experiment to test their predictions, with the restriction that no plate be |

| |exposed for more than 120 seconds. |

|Objectives: |Students will design an appropriate experiment for testing hypotheses/predictions about the effects of |

| |bacterial exposure to UV light as a function of time. |

|Reasons for content and |This day’s instruction provides students an opportunity to make predictions and design an experiment to |

|instructional strategy: |test those predictions—an essential component of the inquiry project. Rather than design a completely |

| |independent inquiry (which could be very overwhelming), students are researching a question I have |

| |provided them. However, I am requiring them to design their own methods of collecting data, thus |

| |affording an opportunity for independent thought. Students will work in groups, creating posters to |

| |facilitate shared understanding between group members and to give students a chance to interact with each|

| |other before beginning the experimental design phase later in the day. |

|Evidence of |Students will verbally present to me their plan for testing UV light exposure times. If their experiment|

|understanding: |will include several data points and a control, I will “certify” their experimental design and permit |

| |them to begin labeling plates. |

|Resources: |Bacterial plates, markers. |

DAY 16: Inquiry Investigation – Conducting the Investigation (50 minutes) – Friday

|What students are doing: |Students will perform their experiment, exposing plates of bacteria to ultraviolet light for different |

| |lengths of time, as determined by students. After students have completed their experiments, there will |

| |be a class discussion considering what different types of data would demonstrate about the research |

| |question. Students will evaluate several different hypothetical graphs, suggesting the implications of |

| |each set of data. |

|Objectives: |Students will test a hypothesis addressing exposure of bacteria to varying amounts of ultraviolet light. |

| |Students will evaluate the meaning of several different types of hypothetical data. |

|Reasons for content and |This day’s instruction allows students to engage in another essential aspect of inquiry-based |

|instructional strategy: |learning—experimentation. For students to understand the nature of science, they need to understand how |

| |to carry out a scientific investigation. |

|Evidence of |Evidence will be provided with the formal lab report at the end of the inquiry investigation. |

|understanding: | |

|Resources: |Incubator, ultraviolet lamp box. |

DAY 17: Inquiry Investigation – Analyzing Data and Representing it as Evidence; and Reconsidering the Model, Coordinating Evidence and Theory, and Presenting Findings (50 minutes) – Monday

|What students are doing: |Students will, in their groups of four, retrieve bacterial plates from the incubator, make observations, |

| |and analyze this data. Students will develop graphs representing their data (bacterial growth vs. |

| |exposure time). Students will determine whether the data fit their predictions and will revise their |

| |hypothesis if appropriate. Students will receive a list of criteria for the written lab reports they |

| |will create (due on Friday). |

|Objectives: |Students will analyze their data and graph results. Students will develop a formal written report |

| |discussing the results of their inquiry experience. Students will reconsider and/or adjust their |

| |hypotheses of the effects of ultraviolet light exposure on bacterial growth. |

|Reasons for content and |This final day of the inquiry investigation asks students to collect and evaluate data to determine |

|instructional strategy: |whether the data support or refute the group’s hypothesis. This aspect of inquiry helps students |

| |understand the need for data representation and analysis—a list of numbers about the experiment means |

| |nothing unless those numbers are logically organized. Asking students to graph their data ensures they |

| |will organize them logically. |

|Evidence of |Students will individually develop a formal report listing their hypotheses/predictions, their |

|understanding: |observations/data, their analysis, and a detailed description and diagram of the mechanism of mutation. |

| |Extensive feedback will be provided. |

|Resources: |Graph paper. |

DAYS 18, 19, and 20: Culminating Project – Students as Genetic Counselors

(190 minutes total) – Tuesday, Wednesday/Thursday, Friday

|What students are doing: |Students will take the role of genetic counselors. Working in pairs, students will receive hypothetical |

| |information from a young married couple expecting their first child. The young wife’s brother has just |

| |been diagnosed with a serious genetic disease (exact type to be determined later), and the wife is |

| |worried she may be a carrier of the trait. The couple wants to know the probability of their child being|

| |affected by the disease. Students will receive descriptions and causes of several genetic diseases, |

| |hypothetical family histories, hypothetical copies of blood tests, and hypothetical gel-electrophoresis |

| |results. Students will be asked to create a pedigree of the family and determine the odds of the faulty |

| |gene being present in the fetus. Students will be asked to provide, along with an analysis of the |

| |family’s genetic lineage, a written explanation of the involved genetic processes—why the gene affects |

| |only certain family members, how the gene is passed from generation to generation, the specific |

| |abnormality in the DNA sequence, and the molecular process (to the level of protein encoding and |

| |function) by which that abnormality causes disease—all in terms that the couple can understand. |

|Objectives: |Students will integrate their knowledge of unit objectives to develop a written product presenting a |

| |summary of the family’s genetic characteristics. |

|Reasons for content and |As with the ethics portion of this unit, my hope is to make genes and DNA as personally-relevant as |

|instructional strategy: |possible. Thus, I will evaluate student learning not through a traditional examination, but rather by |

| |asking students to apply their knowledge of genes and heredity to an authentic case. I want students to |

| |spend time thinking about the information the family needs, and I want to be available to answer student |

| |questions and guide student work, so I will provide three days of class time for students to develop |

| |their summaries. Though students will have to spend some time working on the project at home, the bulk |

| |of their efforts will occur in the classroom, increasing the chances of well-reasoned, complete, and |

| |accurate products. |

|Evidence of |Students will develop an accurate and complete written description of the family’s genetic |

|understanding: |characteristics, meeting the criteria presented with the project. Extensive feedback will be provided. |

|Resources: |Handouts presenting scenario, hypothetical family histories, hypothetical blood tests, hypothetical |

| |gel-electrophoresis results. |

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