Those Genes Don't Fit Like They Used To:
Reviewing New Ideas Emerging in the Fields of Genetics and Heredity
Author: Catherine Hutchings, The New York Times Learning Network. Copyright 2008 The New York Times Company.
Overview Of Lesson Plan: In this lesson, students use the Science Times Special Issue "Beyond the Gene" to explore how recent advancements are leading scientists to rethink the role of genes in the fields of genetics and heredity.
Suggested Time Allowance: 1-2 class periods
Activities / Procedures:
Note To Teacher: In the November 11, 2008, the Special Issue of the Science Times, "Beyond the Gene," the New York Times science writers sought to explain some of the most recent findings about how DNA, genes and heredity work. The gist of what they discovered is that our familiar concepts of genetics and DNA don't begin to explain the complexity of what actually happens within our cells. In short, DNA and genes are being pushed aside as the central players of all inheritance, while the actions of RNA and other molecules are being shown to have a greater role in genetics and heredity than previously thought.
This lesson is designed to help students with a basic understanding of genetics and heredity, as typically presented in high school textbooks, to gain an appreciation for the true complexity of this area of science. For an overview of the topic and articles, listen to the Science Times Podcast with David Corcoran, listed in the Related Times Resources section below, prior to teaching this lesson.
Individually or in pairs, have students use their knowledge of genetics to respond to each of the following prompts. To further engage visual learners include images of each example for students to ponder as they answer the questions.
- "If a pea plant with all yellow seeds is crossed with a pea plant with all green seeds, all of the offspring will have yellow seeds. Why?"
- "A mother has red hair, and so does her child. Why?"
- "Most ‘toadflax' flowers have white petals arranged in a mirror-like symmetry. But some have yellow five-pointed stars. Why might this be?"
After a few minutes, have students share their explanations. As students share their responses, write down key words and phrases they use on the board or overhead. Then discuss their responses: Did students use the word "gene" in their explanations? How would they define the word "gene"? What else do genes do in our cells?
Explain that the first two examples follow the traditional rules of genetics and heredity; traits are controlled by genes with dominant and recessive alleles that affect the phenotype of the offspring. However, the third example of the toadflax flower is more complex. As it turns out, these two flowers with varied colors and symmetry have the same genes. The difference is not in their DNA, but rather in the pattern of methyl group "caps" attached to their DNA and the proteins called histones that the DNA is wrapped around. (The source for this information is today's featured article by Carl Zimmer.) Examples like this are inspiring scientists to rethink the very definition of genes.
As a class, read and discuss the first section of the article "Now: The Rest of the Genome."), focusing on the following questions:
- What is the working definition of "gene" used by scientists since the 1960s?
- Why is scientists' definition of "gene" changing? In other words, why is the gene "in an identity crisis"?
- If "DNA no longer has a monopoly on heredity," what other molecules in our cells might play an important role in determining whether traits are hidden or expressed, or how they are passed from one generation to the next?
- What does the quote by Wilhelm Johanssen, "The word ‘gene' is completely free from any hypothesis," mean? Who was Johanssen, and when in history did he make this statement? Use contextual clues in the article to explain the quote in your own words.
Assign each pair or small group of students a different quote from the New York Times list "Thoughts on Genes.".
(Note: Quotes 1-5 and 10 appear verbatim in the articles, while quotes 6-9 do not. Quotes 6-9 will require students to make inferences from other statements by the scientist quoted along with similar statements on the same subject to put these quotes into context.)
In addition, provide students with copies of the Science Times Special Issue "Beyond the Gene" or print copies of the following articles (if technology is available students may also access the articles online):
- The remainder of the article "Now: The Rest of the Genome."
- The article "The Promise and Power of RNA"
- The article "Scientists and Philosophers Find That ‘Gene' Has a Multitude of Meanings"
Instruct students to use the articles to find the context in which their assigned quote was stated and to relate this quote to scientists' emerging ideas about genetics and heredity. Groups should use the handout ("Beyond the Gene") to guide their discussion and analysis of the quote. It may be helpful to explain to students that this activity is similar to what they did as a class in the last article question, but in greater depth.
Next, have students share their assigned quotes and assessments. As a visual aid, consider enlarging the handout to allow students to create poster-sized charts they can hang around the room. Use the following wrap-up questions to guide students to look at the collection of quotes as a whole. Have students take notes from the class discussion directly onto the handout.
- What common themes or ideas are present in multiple quotes?
- In light of the new findings discussed, do you think genes are less important to geneticists than they once were or not? Why or why not?
- How would you change the definition of "gene" and why?
- What questions do molecular biologists have yet to answer in order to understand the genetic material in human cells?
- How does what you read and learned today expand upon what you already know about genetics and heredity?
For Homework Or Future Classes:
Students find a part of their own textbook that describes a topic related to their quote. For example, students might select a section of text or a diagram related to genes, DNA and RNA, RNA transcription, the genome or protein synthesis. Students should use examples from the articles, their completed handouts and class notes to update the information in their textbooks using one of the following formats: -Write and illustrate a module for a class book. -Make a slide for a class slideshow. -Post on a class wiki which students can access online and use as a supplement to the textbook. For more information on creating a wiki, visit our Teaching With The Times guide Technology Tools: Web 2.0 in the Classroom.
- Science Times with David Corcoran Podcast on genes from November 11, 2008.
- Genetics Glossary
- Graphic: A Bestiary of RNA
- Series: The DNA Age
- Lesson Plan: WAKE UP! There's a Protein for That! Diagramming Protein Synthesis to Illustrate the Science Behind Narcolepsy
- Teaching With The Times: The Human Body
- Student Crossword: Genetics
- Some Biologists Ask 'Are Genes Everything?' Historical article from September 2, 1997.
- DNA (Deoxyribonucleic Acid)
- Genetics and Heredity
- DNA Interactive: Discovering the DNA Structure and Beyond Multimedia resources, learning modules and lesson plans exploring the history and future of DNA research
- "What is a gene, post-ENCODE? Cold Spring Harbor Laboratory Press, History and updated definition" Scientific article on the effects of the ENCODE project on the concept of genes.
- The Why Files: The Grammar of Genetics Article provides a clear, kid-friendly explanation of epigenetics and the role of molecules attached to DNA.