Back to: MICROBIOLOGY 200 LEVEL
Welcome to class!
Hello there, superstar! I’m really glad you’re here, ready to learn something exciting and powerful. Today’s topic is like a magic trick scientists use in the lab to copy and study DNA — it’s all about PCR (Polymerase Chain Reaction) and gel electrophoresis. These two tools are changing lives daily, from solving crimes to diagnosing diseases and even tracing ancestry!
Pcr And Gel Electrophoresis
Have you ever watched a TV crime show where someone says, “We’ll run the DNA test”? That’s PCR and gel electrophoresis at work! These are tools that scientists use to amplify (copy) DNA and then separate it to study. Think of PCR as a photocopier for DNA, and gel electrophoresis as a sieve that helps us sort out the copies based on size.
Let’s break it down so it’s easy to understand and even more fun to learn.
PCR – The DNA Photocopier
PCR stands for Polymerase Chain Reaction. It’s a laboratory method used to make millions of copies of a specific DNA sequence.
Here’s how it works:
Denaturation – The double-stranded DNA is heated to separate it into two single strands.
Annealing – The mixture is cooled to allow primers (short DNA sequences) to attach to the target DNA.
Extension – DNA polymerase adds new nucleotides to form two complete DNA strands.
This cycle is repeated over and over (usually 25–35 times), and in no time, you have millions of copies of your target DNA — like duplicating a document over and over again.
Real-life example: In COVID-19 testing, PCR was used to detect the virus’s genetic material from a small sample. Powerful, right?
Gel Electrophoresis – The DNA Sorter
Once we have the DNA copies, we might want to check their size or compare them to other DNA samples. That’s where gel electrophoresis comes in.
Here’s how it works:
The DNA is loaded into a gel (usually made of agarose, a jelly-like substance).
An electric current is passed through the gel.
DNA, being negatively charged, moves towards the positive end.
Smaller DNA fragments move faster and travel farther, while larger ones move slower.
After some time, you’ll see bands of DNA on the gel, showing you the size and number of DNA fragments.
Real-life example: This technique is used in paternity tests, forensic science, and genetic research.
Summary
- PCR is a technique used to make millions of copies of a specific DNA sequence.
- It involves three steps: denaturation, annealing, and extension.
- Gel electrophoresis is used to separate DNA fragments based on size.
- DNA moves through a gel under electric current, with smaller fragments moving faster.
- These tools are essential in medicine, research, and forensics.
Evaluation
- What does PCR stand for?
- Name the three main steps in a PCR cycle.
- What is the purpose of gel electrophoresis?
- Why do smaller DNA fragments move faster in gel electrophoresis?
- Mention one real-world use of PCR or gel electrophoresis.
Well done, genius! Today, you’ve unlocked the secrets behind some of the most impactful scientific techniques used around the world. With this knowledge, you’re not just learning science — you’re getting ready to change the world. Stay curious, stay focused, and remember — Afrilearn is here to support your journey every step of the way. See you in the next class!