Human Genetic Variation
This module has two central objectives. The
the practice of medicine, and it is vital that citizens
first is to introduce students to major concepts
recognize these changes and are prepared to deal
related to human genetic variation. Homo sapiens
with them. Being prepared involves understanding
comprises a single species, yet the more than
the basic science that underlies new medical
6.9 billion of us alive today, and the millions
practices and therapies and recognizing the
who preceded us following the emergence of fully
complex issues and questions that some of these
modern humans some 150,000 years ago, are a
procedures and therapies raise. Thus, students
diverse lot. One look at the students who sit in
will have the chance to think about how the
your class each day is all you need to confirm
detailed analysis of human genetic variation
that fact. The module’s first objective is to help
is already changing their lives.
students recognize and understand this variation.
If recognizing human variation is common, it is
The second objective is to convey to students the
not new; certainly our ancestors realized that no
relationship between basic biomedical research
two humans are identical. Nevertheless, biologists
and the improvement of personal and public
before Charles Darwin subscribed to what Ernst
health. The knowledge that scientists gained as
Mayr called essentialist thinking: the notion that
they sequenced the human genome is changing
each species is defined by an invariant type that
limits the ability of its members to vary too much
from the essential nature of the species. Among
Darwin’s great insights was the recognition that
the essentialist view is incorrect—the members of
any given species are actually highly variable—
and that some variations within a species will confer
selective advantage on those individuals that possess
them. This variation within species makes
differential selection, and therefore evolution,
possible. Mayr called this view population
thinking, and it pervades modern biology.
Darwin, however, even while working as Gregor
Mendel’s contemporary, was confounded by his
inability to identify the root source of biological
variation or the mechanisms by which those
variations are transmitted to subsequent generations
of organisms within the same species. The
rediscovery of Mendel’s work in the early 1900s
provided those answers, and the reconciliation
of Mendelism and Darwinism in the modern
Figure 1. Humans are a genetically diverse lot. How
synthesis of evolution in the 1930s and 1940s
will understanding this diversity at the molecular level
formed the basis for the biology we practice and
change our lives?
teach today.
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Human Genetic Variation
The identification of DNA as the genetic material
• Studying the genetic and environmental factors
in the early 1940s and the elucidation of its
involved in multifactorial diseases will lead to
structure about a decade later opened the way for
improved diagnosis, prevention, and treatment
an analysis of genetic variation at the molecular
of disease.
level. That analysis proceeds at breakneck speed
• Our growing understanding of human genetic
today, propelled by a host of powerful new
variation will allow us to identify genes
techniques in molecular biology.
associated with common diseases such as
cancer. Genetic testing to identify individuals
This module focuses on our progress in analyzing
who have variations that make them
human genetic variation and the impact of that
susceptible to certain diseases can help people
analysis on individuals and society. There are many
make decisions in uncertain circumstances and
concepts we could have addressed, but we have
holds the prospect for more effective prevention
chosen, with the help of a variety of experts in
and treatment. However, this capability also
this field, a relatively small number for exploration
raises difficult questions about the uses of
by your students. Those concepts follow.
genetic information—questions that illustrate
• Humans share many basic characteristics, but
the personal and social implications of
there is a wide range of variation in human
biological research.
traits. Most human traits are multifactorial:
They are influenced by multiple genes and
We hope the module’s five lessons will be effective
environmental factors.
vehicles for carrying these concepts to your
• The ultimate source of genetic variation
students. Although the activities contain much
is differences in DNA sequences. Most of
interesting information about various aspects of
those genetic differences do not affect how
human genetics, we suggest that you focus your
individuals function. Some genetic variation,
students’ attention on the major concepts the
however, is associated with disease, and some
module was designed to convey. The concluding
improves the ability of the species to survive
steps in each lesson are intended to focus the
changes in the environment. Genetic variation,
students’ attention on those concepts as the lesson
therefore, is the basis for evolution by natural
draws to a close.
selection.
• One of the benefits of understanding human
genetic variation at a molecular level is its
practical value for helping us understand and
treat disease. The development of effective
gene-based therapies is an exciting outcome
of human genetic research. These therapies,
however, are potentially many years away for
many diseases.
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Implementing the Module
The five lessons in this module are designed to be
• to experience the process of inquiry and
taught either in sequence, as a supplement to your
develop an enhanced understanding of the
standard curriculum, or as individual activities
nature and methods of science, and
that support or enhance your treatment of specific
• to recognize the role of science in society
concepts in biology. The following pages offer
and the relationship between basic science
general suggestions about using these materials in
and personal and public health.
the classroom; you will find specific suggestions
in the support material provided for each lesson.
What Are the Science Concepts and
How Are They Organized?
What Are the Goals of the Module?
We have organized the activities to form a conceptual
Human Genetic Variation is designed to help
whole that moves students from an introduction
students reach the following major goals
to human genetic variation ( Alike, But Not the Same),
associated with biological literacy:
to an investigation of its biological significance
• to understand a set of basic scientific principles
( The Meaning of Genetic Variation), to a discussion
related to human genetic variation,
of some of the practical implications of human
Table 1. Conceptual flow of the lessons.
Lesson
Learning Phase
Major Concepts
Lesson 1
Engage
Humans share many basic characteristics, but there is a wide range
Alike, But Not
of variation in human traits. Most human traits are multifactorial:
the Same
They are influenced by multiple genes and environmental factors.
Lesson 2
Explore
The ultimate source of genetic variation is differences in DNA
The Meaning
sequences. Most of those genetic differences do not affect
of Genetic
how individuals function. Some genetic variation, however, is
Variation
associated with disease, and some improves the ability of the
species to survive changes in the environment. Genetic variation,
therefore, is the basis for evolution by natural selection.
Lesson 3
Explain
One of the benefits of understanding human genetic variation at a
Molecular
molecular level is its practical value for helping us understand and
Medicine
treat disease. The development of effective gene-based therapies
Comes of Age
is an exciting outcome of human genetic research. These therapies,
however, are potentially many years away for many diseases.
Lesson 4
Elaborate
Studying the genetic and environmental factors involved in
Are You
multifactorial diseases will lead to increased diagnosis, prevention,
Susceptible?
and treatment of disease.
Lesson 5
Evaluate
Our growing understanding of human genetic variation will allow
Making
us to identify genes associated with common diseases such as
Decisions in
cancer. Genetic testing to identify individuals who have variations
the Face of
that make them susceptible to certain diseases can help people
Uncertainty
make decisions in uncertain circumstances and holds the prospect
for more effective prevention and treatment. However, this
capability also raises difficult questions that illustrate the personal
and social implications of biological research.
3
Human Genetic Variation
genetic variation for the treatment of disease
Despite their current popularity, many teachers
( Molecular Medicine Comes of Age and Are You
think of active, collaborative, and inquiry-based
Susceptible? ), and, finally, to a consideration of
learning rather generically. Defining these three
how understanding human genetic variation
key terms specifically will provide a foundation
can affect the decisions we make about our
on which we can build a detailed description of
own health ( Making Decisions in the Face of
the instructional approach that the five lessons
Uncertainty). Table 1 summarizes the sequence
in this module advocate and implement.
of major concepts addressed by the five lessons.
Conceptually the broadest of the three, active
Although we encourage you to use the lessons
learning means that students are involved in
in the sequence outlined in Table 1, many of
“doing things and thinking about the things
the lessons can be taught individually, to
they are doing” (Bonwell and Eison, 1991, p. 2).
replace or enhance a more traditional approach
These authors elaborate by listing the following
to the same or related content. Table 2 provides
characteristics typically associated with strategies
recommendations for inserting the lessons into
that deserve to be labeled “active”:
a standard high school curriculum in biology.
• Students are involved in more than listening.
• Instructors place less emphasis on transmitting
How Does the Module Correlate
information and more emphasis on developing
with the National Science
students’ skills.
Education Standards?
• Students are involved in higher-order thinking
Human Genetic Variation supports teachers in
(for example, analysis, synthesis, and
their efforts to reform science education in the
evaluation).
spirit of the National Research Council’s 1996
• Students are engaged in activities (for example,
National Science Education Standards (NSES).
reading, discussing, and writing).
Table 3 lists the content and teaching standards
• Instructors encourage students’ exploration of
that this module primarily addresses.
their own understandings, attitudes, and values.
How Does the BSCS 5E Instructional
Most teachers endorse the use of active learning.
Model Promote Active, Collaborative,
We know intuitively, if not experientially and
Inquiry-Based Learning?
explicitly, that learning does not occur through
The activities in this module are designed to
passive absorption. But often, we do not realize
offer students the opportunity to participate in
how active students must be for real learning to
active, collaborative, and inquiry-based learning
occur. Typically, the answer to this question is
in biology. But what do these terms mean?
more active than we might expect.
Table 2. Correlation between lessons and high school biology topics.
High School Biology Topic
Lesson 1
Lesson 2
Lesson 3
Lesson 4
Lesson 5
evolution and natural selection
✔
ethical issues related to genetic testing
✔
✔
✔
✔
and screening
human genetic variation including
✔
genetic disorders
multifactorial traits
✔
✔
✔
✔
✔
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Table 3. Correlation to the National Science Education Standards.
A. The Content Standards
Standard A: As a result of activities in grades 9–12,
Correlation to Human
all students should develop abilities necessary to do scientific inquiry
Genetic Variation
and understandings about scientific inquiry.
• Identify questions and concepts that guide scientific investigations.
Lessons 1, 2 ,and 3
• Use technology and mathematics to improve investigations and communications.
Lesson 2
• Formulate and revise scientific explanations and models using logic and evidence. Lessons 2 and 3
• Recognize and analyze alternative explanations and models.
Lessons 2 and 3
• Communicate and defend a scientific argument.
Lesson 3
• Understanding scientific inquiry.
Lessons 2 and 3
Standard C: As a result of their activities in grades 9–12,
Correlation to Human
all students should develop understanding of the cell and
Genetic Variation
the molecular basis of heridity.
• Cells store and use information to guide their functions.
Lessons 2, 3, and 5
• Cells can differentiate, and complex multicellular organisms are formed as a
Lessons 2 and 5
highly organized arrangement of differentiated cells.
• In all organisms, the instructions for specifying the characteristics of the
Lessons 2, 3, and 5
organism are carried in the DNA.
• Changes in DNA occur spontaneously at low rates.
Lessons 2, 3, and 5
• Species evolve over time.
Lesson 2
Standard E: As a result of activities in grades 9–12,
Correlation to Human
all students should develop abilities of technological design and
Genetic Variation
understandings about science and technology.
• Scientists in different disciplines ask different questions, use different
Lesson 3
methods of investigation, and accept different types of evidence to support
these explanations.
• Science often advances with the introduction of new technologies.
Lesson 5
• Creativity, imagination, and a good knowledge base are all required in the
Lessons 1–5
work of science and engineering.
• Science and technology are pursued for different purposes.
Lesson 5
Standard F: As a result of activities in grades 9–12,
Correlation to Human
all students should develop understanding of
Genetic Variation
• personal and community health.
Lessons 2, 3, 4, and 5
• natural and human-induced hazards.
Lessons 2, 3, 4, and 5
• science and technology in local, national, and global challenges.
Lesson 5
Standard G: As a result of activities in grades 9–12,
Correlation to Human
all students should develop understanding of
Genetic Variation
• science as a human endeavor.
Lesson 3
• nature of scientific knowledge.
Lessons 1–5
• historical perspectives.
Lesson 2
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Implementing the Module
Human Genetic Variation
Table 3. Correlation to the National Science Education Standards.
B. The Teaching Standards
Standard A: Teachers of science plan an inquiry-based
Correlation to
science program for their students. In doing this, teachers
Human Genetic Variation
• develop a framework of yearlong and short-term goals for
Each lesson provides short-term objectives
students.
for students. Tables 1, Conceptual Flow of
the Lessons, and 6, Suggested Timeline for
Teaching the Module, also help teachers plan.
• select science content and adapt and design curriculum to
Using the modules helps teachers update
meet the interests, knowledge, understanding, abilities, and
their curriculum in response to their students’
experiences of students.
interest in this topic.
• select teaching and assessment strategies that support
The focus on active, collaborative, and
the development of student understanding and nurture a
inquiry-based learning in the activities helps
community of science learners.
teachers meet this standard.
Standard B: Teachers of science guide and facilitate learning. Correlation to
In doing this, teachers
Human Genetic Variation
• focus and support inquiries while interacting with students.
All of the activities in the module encourage
and support student inquiry.
• orchestrate discourse among students about scientific ideas.
All of the activities in the module promote
discourse among students.
• challenge students to accept and share responsibility for their All of the activities in the module challenge own learning.
students to accept and share responsibility for
their learning.
• recognize and respond to student diversity and encourage all Combining the BSCS 5E Instructional Model students to participate fully in science learning.
with active, collaborative learning is an
effective way of responding to the diversity of
stu dent backgrounds and learning styles.
• encourage and model the skills of scientific inquiry, as well as Annotations for the teacher throughout the the curiosity, openness to new ideas and data, and skepticism activities provide many suggestions for how that characterize science.
teachers can model these attributes.
Standard C: Teachers of science engage in ongoing
Correlation to
assessment of their teaching and of student learning.
Human Genetic Variation
In doing this, teachers
• use multiple methods and systematically gather data about
Each lesson has a variety of assessment
student understanding and ability.
components embedded within its structure.
Annotations draw teachers’ attention to these
opportunities for assessment.
• analyze assessment data to guide teaching.
Annotations provide answers to questions
that can help teachers analyze student
feedback. The annotations also suggest ways
for teachers to change their approach to
students, based on that feedback.
Standard E: Teachers of science develop communities of
Correlation to
science learners that reflect the intellectual rigor of scientific Human Genetic Variation
inquiry and the attitudes and social values conducive to
science learning. In doing this, teachers
• display and demand respect for the diverse ideas, skills, and
The answers provided for teachers model
experiences of all students.
these qualities.
• nurture collaboration among students.
All the activities are designed to be completed
by students working in collaborative groups.
• structure and facilitate ongoing formal and informal discussion All the discussions in the lessons model the based on a shared understanding of rules of scientific discourse.
rules of scientific discourse.
• model and emphasize the skills, attitudes, and values of
The annotations for teachers provide many
scientific inquiry.
suggestions about how to model these skills,
attitudes, and values.
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The activities in this module were designed with
not involve students in active ex