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MSP:MiddleSchoolPortal/Reproduction and Heredity

From Middle School Portal

Reproduction and Heredity

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Why do I look more like my mother than my father? How come my sister has blond hair, but I have dark hair? How do elephants get so big? Where do babies come from?

Reproduction and heredity are intrinsically interesting topics to middle level students, but they are also abstract and difficult to conceptualize. In response, many teachers facilitate wonderfully active simulations illustrating patterns of inheritance and stages of mitosis, for example. Nonetheless, many students maintain little deep conceptual understanding of the related concepts, even after such direct experiences.

The Life Science Content Standard of the National Science Education Standards for grades 5-8 consists of five fundamental concepts which, when woven together, create a holistic concept of life on earth. They include Structure and Function in Living Systems; reproduction and heredity; regulation and behavior; Populations and Ecosystems; and diversity and adaptations of organisms (NRC 1996, 157).

This resource guide begins with pedagogical suggestions and background content knowledge for middle level educators, because strong pedagogical content knowledge helps teachers increase student understanding of these abstract concepts. Part of the plan is to make explicit how the reproduction and heredity concepts connect to the other four fundamental concepts of the Life Science standard. For example, reproduction occurs at the cellular level and involves subcellular parts, connecting to the structure and function aspect of the standard. The goal is to facilitate student recognition and articulation of these relationships, thus demonstrating conceptual understanding of reproduction and heredity. Further, relevant concepts of the nature and history of science, science in society, and science in technology standards connect to the reproduction and heredity concepts. Following the pedagogy and content knowledge sections are specific lessons, activities and assessments with explicit connections to the standards at the end of the publication.

Background Information for Teachers

Pedagogy

The text of the reproduction and heredity portion of the Life Science Content Standard follows with essential vocabulary words indicated by bold type:

Reproduction is a characteristic of all living systems; because no individual organism lives forever, reproduction is essential to the continuation of every species. Some organisms reproduce asexually. Other organisms reproduce sexually.
In many species, including humans, females produce eggs and males produce sperm. Plants also reproduce sexually—the egg and sperm are produced in the flowers of flowering plants. An egg and sperm unite to begin development of a new individual. That new individual receives genetic information from its mother (via the egg) and its father (via the sperm). Sexually produced offspring never are identical to either of their parents.
Every organism requires a set of instructions for specifying its traits. Heredity is the passage of these instructions from one generation to another.
Hereditary information is contained in genes, located in the chromosomes of each cell. Each gene carries a single unit of information. An inherited trait of an individual can be determined by one or by many genes, and a single gene can influence more than one trait. A human cell contains many thousands of different genes.
The characteristics of an organism can be described in terms of a combination of traits. Some traits are inherited and others result from interactions with the environment (NRC 1996). (Bold type added)

There are 18 essential vocabulary words, a doable number by most accounts. Unfortunately, these words represent only the tip of the iceberg. Science is expressed in very precise terms. Using the appropriate vocabulary matters. Thus, the first resource teachers may want to consult is Developing Science Vocabulary. Help your students learn the vocabulary by using it yourself, often.

Another tool to help you think about the relative importance of concepts and how to sequence lessons is the NSDL Strand Map Service. These maps illustrate connections between concepts and across grade levels. An image of the middle grades (6-8) only part of the DNA and Inherited Characteristics map appears below. Clicking on a concept within the maps will show NSDL resources relevant to the concept, as well as information about related AAAS Project 2061 Benchmarks and National Science Education Standards. Move the pink box in the lower right hand corner of the page to see the grades 6-8 learning goals. Boxes that appear to be floating unconnected connect to concepts in grade bands above or below grades 6-8. You can view the K-12 map at K-12 DNA and Inherited Characteristics. You may also want to view the Variation in inherited Characteristics map.

DNA and Inherited Characteristics

View individual map Printable view of map

Let us look at the content of the standard and identify what students should know before beginning a study in reproduction and heredity. This will help us scaffold and support student learning appropriately. We see the need to address the following characteristic of living things: reproduction as a means of continuing the species, via sexual or asexual means. Thus, students should be able to differentiate between living and nonliving things based on a short, universally agreed-upon list, including a cellular organization and presence of DNA. If they have not already had practice with this, they should do that before moving on to reproduction and heredity. Here is a resource from Teacher's Domain you might find helpful: Living vs. Nonliving.

Students will need to be able to contrast male and female in both plants and animals. They should have a good concept of cell from direct experience observing a variety of cells under a microscope as well as some macroscopic cells like a chicken egg and Nitella, a freshwater algae. The intermodal stem (distance between points on the stem from which multiple "leaves" appear to emanate) is actually a single, nucleated cell. Additional media presentations can help students begin to conceptualize the simultaneous variety and similarity of cells.

Students should be aware that cells contain smaller parts with specific jobs. The cell as a city is a good analogy. Specifically, students should be aware that in cells with a nucleus, the DNA is housed there— a complex, well-organized, molecular structure, and the hereditary information.

Helping middle level students form accurate concepts of eggs and sperm, where they come from, and what they contribute is daunting. It requires the teacher to first have a good grasp followed by formulation of good pedagogical content knowledge. To teach the content well, teachers must be aware of how their own knowledge is organized and, thus, how best to move students through the content to maximize comprehension.

Content Knowledge

History and nature of genetics and heredity

While Gregor Mendel's contributions are certainly important for both their methodology and findings, they are not the only historically significant aspect of genetics and heredity. What were the cultural norms and views in times past? How did those views impact the advancement of science?

History of Genetics Timeline This well-organized table starts with Charles Darwin and Alfred Wallace in 1858, giving teachers a good foundation or review of how knowledge of genetics and heredity developed. However, it is interesting to ponder how people thought about reproduction and heredity prior to Darwin, since those concepts influenced the questions, if any, that were posed.

And Still We Evolve: Section Five: Heredity and Modern Genetics This self-published handbook addresses ancient views (we cannot call them theories since they lacked supportive empirical evidence resulting from rigorous experimentation) of preformation, incapsulation, and epigenesis. Though your students may not admit it, they could have held, or may still hold similar views themselves.

Heredity This page highlights the people and their thinking from the 20th century who advanced understanding of heredity.

A Mendel Seminar A lesson for high school students in advanced biology revolves around Mendel's original paper, Experiments in Hybridization (1865). The structure and support provided in annotations enable the learner to make sense of, and gain insight into, Mendel's reasoning, methods and conclusions.

Thomas Hunt Morgan and Sex Linkage This article summarizes Morgan's work and includes tables and graphics for a clear presentation. It includes a section titled The Context of Morgan's Discovery, from which the following quote is extracted, giving insight into his views:

Morgan, however, had long resisted the idea that genes resided on chromosomes, because he did not approve of scientific data acquired by passive observation. Furthermore, Morgan was not convinced that traits couldn't morph into new forms in an organism based on the blending of parental contributions, an idea leftover from pre-Mendelian scientists. Morgan was sure that . . . researchers who promoted the chromosome theory of inheritance were looking for an easy answer as to how independent assortment occurred in gamete formation, because he believed they ignored counterevidence in the face of excited conviction. In fact, he thought that the concept of genes was at best an invention intended to link the mysterious paths of chromosomes :and discontinuous inheritance patterns.

Sexual vs. asexual reproduction

These two methods of reproduction are sometimes reduced to mitosis vs. meiosis. However, sexual reproduction does not equal meiosis, and asexual does not equal mitosis, as verified in the following resources.

Prokaryotes This nicely organized, "just the facts, m'am" page provides a concise review of prokaryote structure as related to its method of reproduction, binary fission. While binary fission is not considered sexual reproduction, genetic variation is achieved nonetheless.

Mitosis and Cytokinesis This well-organized, user-controlled, comprehensive animation includes a quiz for self- assessment.

Reproduction in Flowering Plants This brief page explains how plants can reproduce asexually and includes labeled photos of the structures involved, such as rhizomes, for example.

Mitosis Glossary Part of a site from San Diego State University for biology teachers.

Meiosis, egg, sperm, and zygote

Understanding that when sex cells form, they carry a specific portion of the parent's genes, and that when fertilization occurs, the fusing of the two parent's cells results in a full complement of genetic material in combinations which never existed before, enables students to better comprehend variation within species, mutations, natural selection and all the mechanisms of evolution. In terms of preparing middle level students for high school biology, emphasis on that concept of new genetic combinations is recommended. It also explains why they do no look exactly like either one of their parents. And, even if they do favor on parent over another, they have a number of other genetic characteristics not easily ob

Meiosis = Double Cell Division A sophisticated animation provides narration in text form and allows the user to control the pace. Appropriate vocabulary is used throughout.

Double Fertilization This plant fertilization animation can be viewed one slide at a time, "step-through," or continuous with narration. Quiz included.

Fertilization in a Sea Urchin This animal fertilization animation can be viewed one slide at a time, "step-through" or continuous with narration. It also has a quiz.

Genes, chromosomes, polygenic traits, and pleiotropy

This section provides resources to support knowledge of gene structure and function.

Heredity and Variation This brief tutorial hits the major patterns of heredity, using appropriate vocabulary to explain observed variation.

Heredity and Traits This page aimed at teachers provides several useful links including What Is Heredity?; What Is a Trait?; a slide show of Observable Traits; Genes & Blood Type; and PTC: The Genetics of Bitter Taste.


Gene Gateway The Gene Gateway is a site to linked to the Human Genome Project. It provides teachers and students access to information regarding human genetic disorders and information provided on each chromosome. Teachers can request a poster showing the placement of genes or use an online version

Cells and DNA This page from the National Institutes of Health has links to the following topics: What is a cell?; What is DNA?; What is mitochondrial DNA?; What is a gene?; What is a chromosome?; and How many chromosomes do people have?.

Polygenic Inheritance This comprehensible, nicely illustrated page presents a thorough description of the polygenic model.

Pleiotropy: One Gene Can Affect Multiple Traits There is not a one-to-one relationship between traits and genes. This article describes the deceitfully simple aspects of pleiotropy.

Does Environment Influence Genes? Researcher Gives Hard Thoughts On Soft Inheritance This article examines the role of environment in gene expression, sometimes called epigenetics.

What Is the Difference Between Genetic Disorders and Infectious Disease? Answers.com provides a concise, black-and-white answer. However, be mindful that susceptibility to infectious disease or acquired disease varies with one's genotype. That is, even identical twins vary in occurrence of acquired disease—one contracts a serious cancer, while the other does not, or one succumbs to a bacteria-borne ulcer and the other does not. Thus, there is a rather blurry line between these two categories of disease. The line seems to becoming further blurred as the fields of proteomics (study of protein interactions) and genomics (study of several simultaneous genes' expression in a given context) grow.

The Nobel Prize in Physiology or Medicine Ever wonder how scientists know the function of a particular gene? The technique used relies on "knocking out" a gene; that is, turning off a specific gene, usually in mice, to see the impact of the one missing gene. The technique earned three men the Nobel prize in 2007. This 11-page document in pdf, prepared for the general public, does an excellent job of describing and illustrating the work of the winners; how each group's work complemented the others'; and finally the implications for the findings, including ethical considerations. Understanding the technique requires a good concept of DNA structure, events in meiosis, and events after fertilization, including mitosis.

Constructing Case Studies for Ethics Teaching After students have acquired understanding of genetics and heredity, they are ready to go beyond the science and consider how the science intersects with everyday life and society. Though some prepared case studies are available, most are geared to higher levels than middle school. This resource provides the basic parameters to help teachers devise a fictional case study to suit student needs.

Lessons and Activities

Modeling DNA Structure This lesson reinforces the location of DNA within cells. Students explore the structure of the DNA molecule and begin to understand how chromosomes, genes, and the base pairs, sugars, and phosphates of the DNA molecule are related. Students view and discuss video segments that describe the role of various genetic units. They also build models of DNA molecules -- using gumdrops, licorice, and toothpicks. At the end of the lesson, they join their model molecules together to form one large strand of DNA.

DNA Interactive This site has an interactive timeline showing the history of genetics from Mendel to modern research. There are also activities that show how DNA works, explaining how it was discovered and how cells build proteins from the genetic code There is also a pdf for a printable origami DNA double helix. There are lesson plans and a variety of other activities on the site. Many of the labs are limited to older students.

Duck Development A three-minute video with suggested discussion questions would be suitable as an illustration of the function of mitosis.

Meiosis: An Interactive Animation This animal cell animation includes crossing over, descriptions of events for each phase, and a list of keywords.

Genetics This nine-page pdf contains a concise introduction to genetics followed by five activities focused on human genetics. First, albinism is used to introduce dominance and recessiveness as well as Punnett Squares. Next, "Coin Genetics" introduces students to the concepts of probability and chance in genetics. Following that students discover why the male/female ratio is about 50/50 in most human populations. The last activity introduces students to pedigrees.

Genetic Traits Database For experience with authentic data, go to this page from Washington University. It allows students to add their own class data on 15 human traits and then to use the pooled data to determine frequencies, see patterns, and decide whether a trait is hereditary. Teachers can extend student experience by constructing activities designed to help students arrive at concepts of dominance and recessiveness, as well as acquired characteristics. Teachers could purposely throw in some acquired characteristics and allow students to discern how their frequencies differ from some heritable traits.

Pasta Genetics This pdf, updated in June 2009, thoroughly describes two activities aimed at upper elementary/middle level learners. Different colored pasta is used to observe patterns of inheritance. Students record data and arrive at conclusions, similar to Mendel's, regarding inheritance of traits through at least three generations.

How Cells Divide: Mitosis vs. Meiosis All cell division is not the same. Cells can divide by mitosis, so each daughter cell retains a full set of chromosomes, or by meiosis, which halves the chromosomes and produces sperm and eggs. Making a baby with the correct number of chromosomes is therefore crucially dependent on meiosis. This Flash feature from NOVA: "18 Ways to Make a Baby" provides a step-by-step, side-by-side comparison of meiosis and mitosis. Suggested use as a means of review and reinforcement.

Cloning Students may have many misconceptions about the process and results of cloning. The Genetics Science Learning Center has a site that explains the process of cloning (What is Cloning?) and an interactive lab that walks through each step of the cloning process as they clone a mouse (Click and Clone). Additional resources include additional web activities, lesson plans and resource guides.

Science and Technology and Society

These resources encourage students to think about the implications of the science associated with genetics and heredity.

Gene Therapy: Molecular Bandage? This page contains four insightful links to help students get beyond the necessarily simple presentation of genetics they have had thus far. Once students understand some traits are inherited, they can begin to understand genetic disorders. At the most fundamental level, persons with a genetic disorder have at least one malfunctioning gene (sources of the malfunction can be many), resulting in lack of a needed protein. So the easy fix is to give the person the protein he is lacking, either directly as in insulin via a pump for diabetics, or indirectly via gene therapy, giving the person the nondefective gene so he can make the needed protein.

WHAT IS GENE THERAPY?
The what and why of gene therapy research.
CHOOSING TARGETS FOR GENE THERAPY
See how researchers decide which disorders are appropriate for gene therapy.
GENE DELIVERY: THE KEY TO GENE THERAPY
Putting therapeutic genes into cells is easier said than done. Find out why.
CYSTIC FIBROSIS: CASE STUDY
An in-depth look at the genetic disorder cystic fibrosis and the application of gene therapy as a potential treatment.

One Strategy for Solving a Moral Problem

This article, directed at teachers, provides a concise process for making decisions and an example. Teachers could modify it for student use, and then have students role-play and simulate a case involving issues such as genetics and privacy or participation in human trials of novel gene therapy.

Gattaca Questions and Teacher Guide This page not only includes a few questions as a study guide for students viewing the science-fiction film but also contains suggestions for other related activities.

Constructing Case Studies for Bioethics Teaching After students have acquired understanding of genetics and heredity, they are ready to go beyond the science and consider how the science intersects with everyday life and society. Though some prepared case studies are available, most are geared to higher levels than middle school. This resource provides the basic parameters to help teachers devise a fictional case study to suit student needs.

SMARTR: Virtual Learning Experiences for Students

Visit our student site SMARTR to find related virtual learning experiences for your students! The SMARTR learning experiences were designed both for and by middle school aged students. Students from around the country participated in every stage of SMARTR’s development and each of the learning experiences includes multimedia content including videos, simulations, games and virtual activities. Visit the virtual learning experience on Genetics.

Careers

The FunWorks

Visit the FunWorks STEM career website for youth to browse related careers in science and medicine!

Assessment

Bikini Bottom Genetics A paper-and-pencil worksheet gives students an opportunity to practice the vocabulary and concepts in Mendelian genetics using the cartoon TV show SpongeBob SquarePants as the context. This resource makes a nice formative assessment; an answer key is provided. The following resource is a useful summative assessment.

Human Pedigrees This Word document gives students practice in interpreting human pedigrees.

Latest Science News from the New York Times

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National Science Education Standards Alignment

The study of genetics and heredity fits well into six of the eight major categories of the content standards. Those six categories and accompanying explanation follow.

1. Unifying concepts and processes in science

As noted in the Introduction, the Life Science Standard of the National Science Education Standards for grades 5-8 consists of five fundamental concepts which, when woven together, create a holistic concept of life on earth.

2. Science as inquiry

When students simulate and critique Aristotle's, Mendel's or Morgan's approaches, they gain insight into the inquiry process. When they participate in modeling simulations in which they make predictions, design a test with a control, record and analyze data, they reinforce the inquiry process.

3. Life science

This connection is already described in the Introduction.

4. Science and technology

So much of what we know about genetics and heredity depends on technological innovation, including microscopy, understanding of enzymes used to "knock out" genes, and the human genome project.

5. Science in personal and social perspectives

Since we are a result of the interactions of genes, there is no separation between genetics issues and personal and social perspectives. Students have specific genetic conditions that may or may not be described as a disorder. They have personal decisions to make regarding their eventual choice to have children who may inherit these conditions. They may have a child of their own with an unexpected genetic disorder and they will need to make important choices then. In addition, society shapes acceptable practices in science to some degree; thus, as members of society students need to gain awareness of the issues and how to think constructively about them.

6. History and nature of science

This one is easily met with discussions of ancient and more modern concepts of patterns in heredity and how those concepts developed. Some were less scientific than others. Students can increase their ability to discriminate science from nonscience through lessons that focus on the history and nature of genetics and heredity.

Read the entire National Science Education Standards online for free or register to download the free pdf. The content standards are found in Chapter 6.

Reference

National Research Council (NRC). 1996. National science education standards. Wasington, DC: National Academy Press.

Author and Copyright

Mary LeFever has taught middle school science and college introductory biology and currently teaches high school biology. She is a doctoral candidate in science education and a resource specialist for the Middle School Portal 2: Math & Science Pathways project.

Please email any comments to msp@msteacher.org.

Connect with colleagues at our social network for middle school math and science teachers at http://msteacher2.org.

Copyright August 2009 — The Ohio State University. This page was updated January 9, 2011. This material is based upon work supported by the National Science Foundation under Grant No. 0840824. Any opinions, findings, and conclusions or recommendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.