Gel Electrophoresis Virtual Lab Worksheet | Exercises Genetics ... - Free Printable

Let’s go step by step to answer each question based on the virtual lab about Gel Electrophoresis.

---

1. What is Gel Electrophoresis used for?

Gel electrophoresis is used to separate DNA fragments (or sometimes proteins) by size. Scientists use it to see how big different pieces of DNA are, which helps in things like identifying genes, solving crimes (DNA fingerprinting), or studying genetic diseases.

---

2. Using the picture to the left, describe how DNA moves through a gel.

In the picture, you can see that DNA starts at the top (near the wells) and moves down through the gel. DNA is negatively charged, so when electricity is turned on, it gets pulled toward the positive end (which is usually at the bottom). Smaller DNA pieces move faster and farther than bigger ones — so they end up lower in the gel. That’s why you see bands at different levels — each band is a group of DNA fragments of the same size.

---

3. What is buffer and what is it used for?

Buffer is a special liquid that fills the gel box. It conducts electricity so the DNA can move through the gel. Without buffer, the electric current wouldn’t flow, and the DNA wouldn’t move. Also, buffer keeps the pH stable so the DNA doesn’t get damaged during the process.

---

4. What is the purpose of the “comb”?

The comb is placed into the gel while it’s still liquid. When the gel hardens and you remove the comb, it leaves little holes called “wells.” These wells are where you load your DNA samples. So the comb makes space for your samples to sit before the electricity turns on.

---

5. Label the following on your bench.

Looking at the diagram:

- A → This is the micropipette. You use it to suck up and drop small amounts of liquid (like DNA samples).
- B → This is a tube with blue liquid — likely the DNA sample mixed with loading buffer.
- C → Another tube — probably contains another DNA sample or maybe a marker/ladder.
- D → A third tube — could be another sample or control.
- E → This is the gel box (also called electrophoresis chamber). It holds the gel and buffer, and has electrodes to run the current.
- F → Already labeled: Pipette tips (used with the micropipette).

So fill in:

A → Micropipette
B → DNA sample (with loading buffer)
C → DNA sample or ladder
D → DNA sample or control
E → Gel box / Electrophoresis chamber

*(Note: In many labs, B, C, D might be different samples or standards — but since no labels are given, we describe them generally as sample tubes.)*

---

6. What are the two major functions of “Loading Buffer?”

Loading buffer does two important things:

1. It adds color – so you can see where your DNA sample is going when you load it into the well. Without color, it would be invisible!
2. It makes the sample heavy/dense – so when you put it in the well, it sinks to the bottom instead of floating away. Some loading buffers also have sugar or glycerol to make them thick.

*(Bonus: Sometimes it also contains a dye that moves with the DNA so you know when to stop the run.)*

---

Final Answer:

1. Gel electrophoresis is used to separate DNA fragments by size.
2. DNA moves from the negative end (top) to the positive end (bottom); smaller pieces move faster and farther.
3. Buffer conducts electricity and keeps pH stable so DNA can move safely through the gel.
4. The comb creates wells in the gel to hold DNA samples.
5.
- A: Micropipette
- B: DNA sample tube
- C: DNA sample or ladder tube
- D: DNA sample or control tube
- E: Gel box (electrophoresis chamber)
6. Two functions of loading buffer:
1. Adds color so you can see the sample.
2. Makes the sample dense so it sinks into the well.