This is a Making Thinking Visible strategy that I like to use to start a unit. To start our 7th grade genetics and heredity unit, each student built a DNA molecule. This molecule is the foundation to the unit, as well as other following units in life science: Evolution and the Human Body. Students research the basics of the molecule structure as they build, but then are encouraged to randomly place down the nucleotide pairs as the rungs (adenine, thymine, guanine, cytosine.) It's the randomness of these rungs is what ultimately account for everyone's DNA to be identical and give us our unique traits. This is the foundation of the unit and can be framed as our essential question, "How is an organism’s variation reflects heredity due to the nature of genetics?" Students hang their DNA molecule above their desk to show its unique properties as as a visual as we refer to it frequently for the remainder of the year.