Classroom activity

7. Flower and Frog Dissection

Sarracenia flower dissection: Image courtexy of Noah ElhardtSarracenia flower dissection: Image courtexy of Noah Elhardt Leopard frog in duckweed: Image courtesy of Steven DunlopLeopard frog in duckweed: Image courtesy of Steven Dunlop

Summary
To learn about the structure and function of living things, it is essential to explore the anatomy of real organisms up close and personal. While much can be accomplished by studying living things and their life cycles (see Raising Plants and Raising Trout projects), dissections offer a view of the internal structures and how they contribute to the whole. What follows are resources and information for teachers interested in conducting a flower and/or frog dissection. There are many excellent lesson plans and dissection guides on the web already. Rather than recreate these resources here, My Science Box provides nitty-gritty logistics and resources such as a selected list of great web resources, how to order frogs, what equipment you need, student handouts, and teaching strategies.

6. Cell Energy - Plant Pigments

Chlorophyll extractionChlorophyll extractionSummary
Chlorophyll is the pigment in plants that captures sunlight energy and uses it to drive photosynthesis. While chlorophyll does give plants their characteristic green color, chlorophyll actually comes in many colors and subtypes ranging from green to yellow to orange to red. In this experiment, students use paper chromatography to separate the many pigments from one another. First the pigments are extracted from the plants by simply crushing the plant cells open on the filter paper with the edge of a penny. When the filter paper is then immersed in rubbing alcohol, the pigments are carried upwards through capillary action. The smallest pigments travel more quickly and thus separate from the larger pigments that remain closer to the origin line.

5. Slimy cells

Summary
To solidify students’ conceptualization of cells, students build a model of a cell in a ziplock bag using polyvinyl alcohol slime as cytoplasm. So far, students’ experience with cells has been 2 dimensional – diagrams and microscopic slides. The 3 dimensional nature of cells comes to life as students use everyday objects to represent the many parts of a cell. In addition, students can use this activity to develop a sense of scale, calculating how big a human would be if the ziplock bag cell model were really the size of a cheek cell.

1. Is it alive?

Summary
What does it mean to be alive? Is a cactus alive? Is a seed alive? Is the air we breathe alive? What are the necessary characteristics? To hook students into the question, they are introduced to “glue monsters” (sometimes known as “scooting glue”) and the class discusses whether the “monsters” are alive or not. Next, students are given cards with the names of various objects and asked to sort them into categories: alive, once was alive, never alive, and not sure. Finally, students create a list defining the characteristics of life – a set of characteristics that all living things share. The list is initially developed in pairs, then in larger groups of 4, and ultimately as a whole class. The final list is turned into a poster that can be referenced and modified throughout the remainder of the unit as students learn more about what it takes to be alive.

7. DNA Fingerprinting

DNA adding tapeDNA adding tapeSummary
In this CSI activity, students solve a mystery using “DNA” taken from the scene of the crime. This write up describes how to collect a “DNA sample” (student invented DNA sequence on adding machine tape) from the culprit and from each person in the class, then run the DNA on a “gel” that covers the floor of the classroom, a hallway, or gymnasium. Naturally, the CSI aspect can become as elaborate as you wish by including additional “clues” such as fingerprints, a ransom note written in a specific type of ink, cloth fibers, eyewitness accounts and more. Since both DNA fingerprinting and paper chromatography (see Sources for lesson plans) rely on the same principles – separating molecules by size – a crime scene in which there is both a note written in a specific type of water-based ink as well as a DNA sample that may compared to the students’ DNA draws some interesting parallels conceptually between these two CSI techniques.

6. Protein Factory

Summary
Using a DNA model like the one created in the DNA Models lesson, students take on the role of various parts of the cell in order to model the process of protein synthesis. Each student receives a card describing, step by step, what s/he should be doing. In a class of 30:

  • RNA codons: each 3 nucleotide codon in this mRNA molecule has been highlightedRNA codons: each 3 nucleotide codon in this mRNA molecule has been highlighted4 students are DNA. They help the RNA polymerase unzip the double stranded DNA and zip it back together again once it has been transcribed.
  • 1 student is RNA polymerase. S/he identifies a promotor sequence, reads one strand of DNA, finds the matching RNA nucleotide, and assembles the messenger RNA.
  • 4 students are messenger RNA. They assemble RNA nucleotides and carry the finished messenger RNA molecule out of the nucleus to the ribosome.
  • 1 student is the ribosome. S/he identifies the AUG start sequence, reads the messenger RNA, finds the matching transfer RNA, and assembles a protein.
  • 20 students are transfer RNA. Each is assigned a different amino acid and assembles transfer RNA molecules for the ribosome. When the amino acid is removed, the students removes the empty transfer RNA.

5. Secret Codes

Example secret DNA codeExample secret DNA code

Summary
Kids love secret codes and secret messages. In this activity, kids first discover how codes work by reading and writing secret messages written in Morse code. Next, they make up their own secret codes and trade messages written in their self-created code. Finally, students learn how DNA codes for a “secret” protein message in a two step coding system – the genetic code. Since each of the 20 amino acids has a one letter abbreviation, student can discover the secret protein “messages” encoded in a DNA strand. Several secret DNA messages are provided for students to decode under the assessments section. For homework, students can be challenged to write a secret message to a friend using the genetic code.

Objectives
Can explain how DNA codes for a sequence of amino acids.
Can begin to explain some of the differences between DNA and RNA.
Can begin to describe the process of transcription and translation.

Vocabulary
DNA
Messenger RNA
Ribosome
Amino acids
Protein
Codon
Morse code
Genetic code
Transcription
Translation

4. DNA Models

Summary
DNA structure: click on the image to see it rotateDNA structure: click on the image to see it rotateIn this activity, students “discover” the structure of DNA by playing with puzzle pieces representing the component pieces of the DNA molecule: the sugar deoxyribose, phosphate groups, and the 4 nucleic acids (adenine, thymine, cytosine and guanine). The process the students go through in putting the puzzle together resembles the way James Watson and Francis Crick deduced the molecular structure of DNA by manipulating molecular models of the component pieces (and a heavy reliance on the prior experimental work of Rosalind Franklin, Maurice Wilkins, and Erwin Chargaff). The model created by the students makes a lovely classroom decoration and reference for discussing DNA replication, transcription and translation.

2. Making Babies

Summary
This is an extension of the Human Traits survey activity designed to introduce students to genes, genotypes, and simple inheritance patterns. Using information from the Human Traits Survey, students make guesses about their own genotype, create gametes from their genotypes, then make “babies” with a partner. Along the way students discover answers to the questions: What are genes? How are genes (and traits) passed on? How are gametes different than other cells in our body? Why do I look like mom in some ways and dad in other ways and neither of them in still other ways? Why don’t siblings look alike?

1. Human Traits

Summary
Genes and DNA are very abstract concepts for students. In order to "hook" them in, I open my genetics and evolution unit with human genetics, specifically looking at the variations in human traits. This allows students' natural curiosity about their identity to draw them into the study of heredity. There are lots of great single gene traits with simple dominance inheritance patterns to explore: earlobe attachment, tongue rolling, cleft chin, etc. There are some polygenic traits that can be explored: hair color, eye color, reach, reaction time, etc. Hair texture (curly, wavy, vs. straight) offers a good example of incomplete dominance. After collecting information from themselves and two others, the population data is collected on several large charts in order to look for and discuss the patterns.