What is it?

• PCR is like a copy machine for DNA. It replicates DNA automatically.
• Only a tiny amount of DNA is needed. Imagine if a grain of rice could feed an entire town!

How does it work?

• Uses a PCR machine aka a thermal cycler or thermocycler because it changes temperature. 🌡️
• Each cycle doubles the DNA.
• You can put a mix of DNA sequences in, but only chosen sequences get copied. It's like selecting which photos to print!

What's needed for this magic?

• Primers: These are like DNA's starting line. They decide which sequences get copied.
• Ideal size: 18-30 nucleotides.
• Taq DNA polymerase: A super special enzyme from a bacteria named Thermus aquaticus that lives in hot springs. Ever heard of Yellowstone National Park? That's where you'd find this little guy! Why is it cool? Most enzymes would "melt" in the hot waters, but not this one!
• DNA nucleotides: These are the building blocks for making the DNA copies.

Result?

• Loads of specific DNA sequences in a short time.
• The bigger PCR machines are like mega theaters - they can replicate DNA in over 100 samples at once!

Purpose: Sometimes, you need to sort DNA by their lengths.

Setting it up

• A sheet of gel (3-4mm thick). It's like a mini mattress.
• This gel has "wells" or pockets near one end.
• Place the gel in a tank with two electrodes and pour an electrolyte solution over it.
• Put a DNA sample in each well. Think of it as adding racers to their starting blocks!

Go, DNA, Go! 🏁

• Apply voltage across the electrodes.
• DNA is negatively charged (thanks to phosphate chains) and runs towards the positive end. It's like the finish line for the DNA race!
• The gel slows down the DNA. Small DNA fragments race faster than big ones.

Results?

• Turn off voltage after some time.
• Add dye to the gel to see the DNA (kinda like coloring in a drawing).
• DNA that’s the same length will form bands (like race finish lines).
• More bands mean more DNA sizes were in your sample.
• The rightmost lane is the “ladder”, a reference with known DNA lengths. It's like a measuring tape for DNA!