DNA & You
In Part 1 you found the nucleus, the vault where DNA is stored. Now you'll break that vault open, pull the DNA out until you can see it, read a real DNA sequence, and use it to crack a case.
The smoothie shop "Berry Bliss" is famous for its strawberry smoothies. Then a customer, Ms. Johnson, posted online accusing the shop of secretly using raspberries and lying about it. The owner, Mr. Patel, fired back and swears he uses only fresh strawberries. It's blowing up online. A team of high school science students, you, steps in to settle it with the one thing that can't lie: DNA.
You can't identify a berry from DNA you can't reach. First job: get the DNA out of the smoothie sample and make it visible. Watch the video, then follow the picture guide step by step.
Dish soap dissolves the greasy membranes around the cell and the nucleus, spilling the DNA out. Salt makes the DNA strands clump together. DNA can't dissolve in cold alcohol, so it falls out of the liquid as a visible white tangle. Strawberries are octoploid, eight full sets of chromosomes per cell, which is exactly why you can see this with your eyes when you couldn't from your cheek swab.
The lab sent back a DNA sequence from the smoothie sample. Every color is one letter of the genetic code. Read the evidence, then build the molecule out of candy so you can see how it fits together.
Each peak below is one base. Use the color key to read the sequence left to right, and write the letters in your notebook.
Build your sequence as a candy double helix:
Model concept: Svenja Lohner / Science Buddies.
A always pairs with T. C always pairs with G. That's how the two sides lock together. Watch this, then use it.
You only decoded one side of the ladder. Use the pairing rule to figure out the entire other strand, then build it. If your first strand starts A-G-C, the partner strand must start T-C-G. Finish the helix.
Post your candy DNA to The Wall, first name in the Subject line.
You proved it's strawberry. But Ms. Johnson isn't done: now she says the "protein-packed" label is a lie too. Time for a chemistry test that turns purple when protein is there.
Biuret reagent is caustic and will burn skin and eyes. Do not touch it, do not taste anything, keep it off your skin. If it touches you, rinse with water right away and tell your teacher. Your teacher handles the reagent bottle.
Compare your smoothie tube to the Control. What's the verdict on Ms. Johnson's second claim?
Proteins are chains of amino acids linked by peptide bonds. The copper in biuret reagent reacts with those bonds and turns purple. More protein, deeper purple. No peptide bonds, no color change.
Milk, juice, sports drink, protein shake. Predict first, then test. Which has the most protein?
You extracted a berry's DNA and read its code. But the most interesting genome in the room is yours. Some of your traits are written right into your DNA. Run the checklist on yourself and tally your Genetic Selfie.
Go around the room and count hands for each trait. Even with just these six, almost nobody has the exact same combo. That's six traits. Your real DNA runs about 20,000 genes. That's why, unless you have an identical twin, there is no one else on Earth built from your exact code.
Old textbooks said each of these is one simple gene. Scientists now know that's mostly a myth. Tongue rolling, earlobes, and most of your traits are actually a team effort of many genes plus your environment. The simple version is fun. The true version, that you are the product of thousands of genes working together, is way cooler.
Forensic DNA analyst (the job you did today), genetic counselor, geneticist, biotech researcher. Reading and using DNA is a real career, and it starts with exactly what you did this morning.
Scan to upload. DNA extraction, candy helix, protein tubes, your Genetic Selfie. It all goes here.
Put your first name in the Subject line.
You pulled DNA out of a cell, read its code, tested it for protein, and met your own genome. Ms. Johnson has been answered. Nice work, forensic team.