Project - Snail Variations

Variation in a population is the raw material on which natural selection works. How do scientists measure and quantify variation in traits? We use garden snails as a model organism in order to describe and measure several different traits. Groups are given a small population of snails and must devise an objective way to measure a trait of their choosing (length, mass, speed, color intensity, stripes, withdrawal reflex reaction time, number of pennies it can carry, etc.). There are many ways to extend this activity. For instance, scientific protocols may be traded between groups, hypotheses may be made concerning what individuals will survive better in different environments, and snails may be tagged and released into one or more environments and the populations monitored over time. A long term open-ended project such as this provides a natural extension and assessment opportunity for both evolution and ecology concepts.

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.

Assessment - Comic Strip

Protein synthesis comic strip: Created by teachers from the Science STARTS/Delta Sierra Science Program summer instituteProtein synthesis comic strip: Created by teachers from the Science STARTS/Delta Sierra Science Program summer institute


Let your creative juices flow. The process of translating nucleic acids into amino acids becomes a tale of suspense, drama and adventure as you come up with a Marvel Comics style adventure story that is an analogy for protein synthesis. Draw comparisons between DNA and a secret message written in code. Compare ribosomes to factories churning out products. Students will surprise you with the crazy analogies they can come up with and the elegant stories they can spin.

Reinforce and assess students’ understanding of the central dogma of molecular biology.

Genetic code
Base pair
RNA polymerase
Messenger RNA
Transfer RNA
Amino acid

6. Protein Factory

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

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.

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.

Messenger RNA
Amino acids
Morse code
Genetic code

4. DNA Models

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.

3. DNA Extraction

Strawberry DNA: The cloudy substance in the upper layer is strawberry DNA.Strawberry DNA: The cloudy substance in the upper layer is strawberry DNA.Summary
What is DNA? What does it look like? In this activity, students extract DNA from strawberries using diluted dish soap and alcohol. Suddenly this mysterious secret of life can be seen materializing out of strawberry juice right in front of students’ eyes. The long tangled DNA strands that ultimately form may be collected using a bamboo skewer or glass stirring rod. The DNA may even be saved in a necklace made from an eppendrof tube, alcohol and string.

2. Making Babies

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

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.

Genetics Box

This box hooks students into the study of genetics by investigating the inheritance of human traits. Drawn by students' natural curiosity about how they come to look the way they do, they learn the basics of Mendelian genetics. From this introduction, students extract DNA, build DNA models and use them to study replication, transcription and translation.