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 90minute period, so the unit will span a total of fifteen 50-minute periods and five 90minute 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
Students will engage in an introductory dialogue about genes, DNA,
are doing:
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
Before beginning a unit on genes and heredity, it’s important that
content and
students achieve a basic understanding of the reasons for learning about
instructional
the topic. Students need a broad picture of the role of genes and
strategy:
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
understanding: will serve as a baseline for 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
Students will read a historical physician’s report describing a patient
are doing:
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
A real-life genetic disease provides students an authentic interface for
content and
beginning their learning about the role of genes and heredity in life. By
instructional
synthesizing authentic written descriptions and physical observations of
strategy:
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,
understanding: integrating observations of blood 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
Students will listen to brief direct instruction discussing restriction
are doing:
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
This day’s activities build on the prior day’s discovery of the sickle-cell
content and
disease, providing a further opportunity for students to identify the role
instructional
of genes and heredity in life. The day provides an opportunity for
strategy:
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 gelelectrophoresis gives them practice developing scientific hypotheses.
Evidence of
Students will use a model for understanding restriction enzymes,
understanding: working in pairs to complete a worksheet 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
Students will perform the gel-electrophoresis procedure on known and
are doing:
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
As yesterday, this day’s activities build on the prior day’s discovery of
content and
the sickle-cell disease, providing a further opportunity for students to
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identify the role of genes and heredity in life. Further, the day provides
strategy:
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 gelelectrophoresis 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
understanding: the lab, they will analyze 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
Students respond to a variety of ethical dilemmas, beginning with a
are doing:
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 atrisk 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
It’s very important to me that students take a personal interest in genes
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and DNA—I want them to understand how these “invisible” concepts
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relate to daily life. I believe that by presenting students with a realstrategy:
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
understanding: and write five brief statements about 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
Students use a model to discuss, in groups, appropriate solutions to an
are doing:
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
Students may have felt overwhelmed trying to determine the proper
content and
course of action for the dilemmas presented yesterday; today’s
instructional
instruction provides students with a tool for thinking about ethical
strategy:
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
understanding: drawn—providing the character’s 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
Students are told they’ll be making a real-life ethical decision today.
are doing:
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
Ethics could be a very intangible topic for students; today’s activity
content and
allows students to experience the meaning behind ethical decisions.
instructional
This class serves as a summary for the bioethics mini-unit, integrating
strategy:
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
understanding: beliefs changed and how they used 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
Students will be presented with the concept of pedigrees as models of
are doing:
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
Now that students have a basic knowledge of the effects of faulty genes
content and
on humans (through their experiences with sickle-cell anemia and
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Huntington’s disease), they are ready to describe disease using a
strategy:
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
understanding: family tree they created earlier.
Resources:
Descriptions of various families on transparencies.
DAY 9: Punnett Squares as Models for Inheritance (50 minutes) -- Monday
What students
Students will compare their physical features with those of their
are doing:
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 codominance
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
Introducing Punnett squares at this point in the unit allows students to
content and
build on their knowledge of genetics gained through their experience
instructional
with sickle-cell anemia, Huntington’s disease, and pedigrees. Rather
strategy:
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
understanding: pairings, beginning with features 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
Students will begin by working in groups to create a large model of
are doing:
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
Every biology textbook diagrams the structure of DNA, but these
content and
diagrams often seem a poor representation of the actual DNA molecule.
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I believe that by helping students create their own physical model of
strategy:
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
understanding: paper, writing the function of the 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
Students will begin by deciphering a code (composed of only the letters
are doing:
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
The Central Dogma is perhaps the most important concept in modern
content and
biology (only evolution might be more important), yet few students
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understand it,—I think because they never get to actually “experience”
strategy:
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
understanding: discovering the encoded word. Students 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
Students will discuss how a single fertilized egg can grow into an entire
are doing:
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
Just as with transcription and translation, I believe students need to
content and
actively perform the process of replication if they are going to gain a
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solid understanding of the concept. By replicating a single piece of
strategy:
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
understanding: asked to write the complimentary 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
This day’s instruction begins by returning to the mutation present in the
are doing:
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
Students will best understand the different types of mutation by
content and
actually examining the changes each mutation causes in amino acid
instructional
sequence. This will provide students with knowledge of how mutations
strategy:
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 microscale topics of instruction of the past week.
Evidence of
Students will be provided with a worksheet listing several “normal”
understanding: and “mutant” DNA sequences, and 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
Students will conduct a short inquiry project on the effects of
are doing:
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.
Objectives:
Reasons for
content and
instructional
strategy:
Evidence of
understanding:
Resources:
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.
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.
Inquiry enables students to engage in the most authentic of scientific
activities—experimentation. 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.
Students will apply their knowledge of transcription and translation to
determine the amino acid sequence 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.
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
Students will discuss, in the same groups of four, the amino acid
are doing:
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
This day’s instruction provides students an opportunity to make
content and
predictions and design an experiment to test those predictions—an
instructional
essential component of the inquiry project. Rather than design a
strategy:
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
understanding: exposure times. If their experiment 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
Students will perform their experiment, exposing plates of bacteria to
are doing:
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
This day’s instruction allows students to engage in another essential
content and
aspect of inquiry-based learning—experimentation. For students to
instructional
understand the nature of science, they need to understand how to carry
strategy:
out a scientific investigation.
Evidence of
Evidence will be provided with the formal lab report at the end of the
understanding: inquiry investigation.
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
Students will, in their groups of four, retrieve bacterial plates from the
are doing:
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
This final day of the inquiry investigation asks students to collect and
content and
evaluate data to determine whether the data support or refute the
instructional
group’s hypothesis. This aspect of inquiry helps students understand
strategy:
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
understanding: hypotheses/predictions, their 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
Students will take the role of genetic counselors. Working in pairs,
are doing:
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
As with the ethics portion of this unit, my hope is to make genes and
content and
DNA as personally-relevant as possible. Thus, I will evaluate student
instructional
learning not through a traditional examination, but rather by asking
strategy:
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 wellreasoned, complete, and accurate products.
Evidence of
Students will develop an accurate and complete written description of
understanding: the family’s genetic 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.