The Code Breakers: How Repton's Science Society is Editing the Very Book of Life

Students at the Repton School Science Society are getting a first-hand look at the revolutionary field of gene editing through hands-on CRISPR-Cas9 experiments.

Published: October 2023 Repton Science Society CRISPR, Gene Editing

Imagine if you could find a spelling mistake in a recipe book and, with a pair of microscopic scissors and a pencil, neatly cut out the wrong word and write in the correct one. Now, imagine that recipe book is the DNA of a living organism, and the recipe is for life itself. This isn't science fiction; it's the revolutionary field of gene editing, and students at the Repton School Science Society are getting a first-hand look at this powerful technology.

For their flagship project, the society has embarked on a mission to demonstrate the core principles of CRISPR-Cas9, the most precise gene-editing tool ever developed. Their target? A simple bacterium, E. coli. Their goal? To deactivate a single gene, making the bacteria resistant to a common antibiotic. This experiment is more than a school project; it's a window into a future where genetic diseases could be cured, crops could be fortified against climate change, and our understanding of biology is fundamentally rewritten .

"This experiment is more than a school project; it's a window into a future where genetic diseases could be cured, crops could be fortified against climate change, and our understanding of biology is fundamentally rewritten."

The Blueprint of Life: A Quick Primer

Before we dive into the experiment, let's break down the key concepts.

DNA

Think of DNA as the intricate instruction manual for building and operating an organism. It's written in a chemical code made up of four "letters" – A, T, C, and G.

Genes

These are specific "chapters" or "recipes" within the DNA manual. Each gene provides the instructions for making a protein, which does a specific job in the cell.

CRISPR-Cas9

This is the revolutionary "search-and-replace" tool with two components: the "Search Engine" (Guide RNA) and the "Molecular Scissors" (Cas9) .

Step 1: Search

The custom-made guide RNA locates the specific target sequence in the DNA.

Step 2: Cut

The Cas9 enzyme cuts the DNA double helix at the precise location identified by the guide RNA.

Step 3: Repair

The cell's repair machinery fixes the cut, allowing scientists to disable genes or insert new genetic material.

The Repton Experiment: A Step-by-Step Guide to Gene Editing

The society's project aimed to disrupt the lacZ gene in E. coli. This gene allows the bacteria to digest a specific sugar, turning their colonies blue in the presence of a special dye. By successfully editing this gene, the students would prevent this colour change, creating a visual confirmation of their success.

Laboratory setup for gene editing experiment
The laboratory setup used by Repton students for their CRISPR experiment.

Methodology

The students designed a custom "guide RNA" that would specifically target the lacZ gene sequence. This, along with the Cas9 protein, was ordered from a biotech supplier.

Two batches of E. coli bacteria were prepared. One would receive the CRISPR-Cas9 machinery (the experimental group), and the other would not (the control group).

The CRISPR-Cas9 components were introduced into the experimental group of bacteria using a process called "heat shock." This temporarily makes the bacterial membranes porous, allowing the editing tools to enter the cells.

Both batches of bacteria were spread onto agar plates containing the special blue dye and an antibiotic. They were then left overnight in an incubator to grow.

The next day, the students observed the results. A successful edit would be visible to the naked eye.

Key Reagents & Materials

Reagent / Material Function
CRISPR-Cas9 Plasmid A circular piece of DNA engineered to carry the instructions for making the Cas9 protein and guide RNA inside the bacterial cell.
Agar Plates with X-Gal The growth medium. X-Gal is the dye that turns blue when digested by the product of the functional lacZ gene.
Competent E. coli Cells Bacteria specially treated to be ready to take up foreign DNA during the "transformation" step.
LB Broth (Luria-Bertani) A nutrient-rich liquid food used to grow the bacteria before and after the transformation process.
DNA Gel Electrophoresis Kit A toolkit used to separate DNA fragments by size, allowing the students to visualize and confirm the results of their PCR.

Results and Analysis: A Clear-Cut Success

The results were strikingly clear. The control plate, which did not receive the CRISPR machinery, showed thriving colonies, all of which were blue. This confirmed that the bacteria's lacZ gene was fully functional.

The experimental plate, however, told a different story. While many colonies grew (white and blue), a significant number were pure white. These white colonies had successfully had their lacZ gene disrupted by the CRISPR-Cas9 system. They could no longer digest the sugar, and therefore, could not turn blue. The students had successfully edited the genome of a living organism.

Colony Analysis

Plate Type Total Colonies Blue Colonies White (Edited) Colonies Editing Efficiency
Control 250+ 250+ 0 0%
Experimental 180 95 85 47.2%

This table shows a strong correlation between the application of the CRISPR-Cas9 system and the appearance of white, gene-edited colonies, with an editing efficiency of nearly 50%.

PCR Confirmation

Sample Target Gene PCR Product Size (Intact Gene) PCR Product Size (Edited Gene) Result
Blue Colony lacZ 3000 bp No product Gene Intact
White Colony lacZ No product 1500 bp Gene Disrupted

The students used PCR, a DNA photocopying machine, to confirm the physical change in the DNA. The smaller product from the white colony confirmed a large piece of the lacZ gene had been deleted.

Bacterial colonies showing gene editing results
Example of bacterial colonies showing both edited (white) and unedited (blue) colonies after CRISPR treatment.

Gene Editing Efficiency

47.2% Success Rate
0% Editing Efficiency 100%

Beyond the Petri Dish: The Future is Now

The Repton School Science Society's project is a microcosm of a global biological revolution. The same principles they demonstrated are being used in labs worldwide to develop therapies for sickle cell anaemia, create malaria-resistant mosquitoes, and engineer crops that can withstand drought .

Medical Applications

CRISPR is revolutionizing medicine with potential treatments for genetic disorders like sickle cell anemia, cystic fibrosis, and Huntington's disease.

Agricultural Innovation

Gene editing is creating crops with improved yields, disease resistance, and enhanced nutritional content to address global food security challenges.

Research Tools

CRISPR enables precise genetic modifications in model organisms, accelerating basic biological research and drug discovery.

Educational Impact

This hands-on experience does more than just teach technical skills; it fosters a deep understanding of the immense power and profound ethical responsibilities that come with gene editing. The students at Repton aren't just learning science from a textbook. They are, quite literally, getting their hands on the tools that are shaping our future, one precise cut at a time.