Selectable marker facts for kids

A selectable marker is like a special tag that scientists add to a cell when they want to put new DNA inside it. This tag helps them easily find the cells that successfully received the new DNA.

Scientists often use selectable markers when working with bacteria or cells grown in a lab dish (called cell culture). These markers are super helpful because they show if a process called transfection (which means putting foreign DNA into a cell) worked. It's a key tool in gene targeting, where scientists aim to change specific genes, or in gene knockout, where they turn off a gene.

What Are Selectable Markers?

A selectable marker is a special gene that scientists add to a cell along with another gene insert they are interested in. Think of it as a helpful signal. If the cell takes in the new DNA, it also takes in the marker. This marker then gives the cell a new ability, which scientists can easily detect.

How Do They Work?

Most of the time, selectable markers are genes that make cells resistant to something harmful, like an antibiotic. Here's how it works:

Finding the Right Cells

1. Scientists try to put new DNA into many cells. 2. After this, they grow all the cells on a special plate that contains an antibiotic. 3. The antibiotic will kill any cells that did not get the new DNA and the selectable marker. 4. Only the cells that successfully took in the new DNA (and the marker) will survive and grow because the marker makes them resistant to the antibiotic. 5. These surviving cells form visible groups called colonies. This tells the scientists that these cells have the new genetic material they wanted to introduce.

What About Screenable Markers?

There's also something called a screenable marker. While a selectable marker helps you select for the cells you want (by killing the unwanted ones), a screenable marker lets you see the difference between wanted and unwanted cells. For example, a screenable marker might make the cells glow a certain color, so you can easily pick out the ones that got the new DNA.

Cool Examples of Selectable Markers

Here are some common selectable markers that scientists use:

• Beta-lactamase: This gene helps bacteria become resistant to an antibiotic called ampicillin. If bacteria have this gene, they can grow even when ampicillin is present.
• Neo gene: This gene comes from a tiny piece of DNA called Tn5. It makes bacteria resistant to an antibiotic called kanamycin. In more complex cells, like those from plants or animals (called eukaryote cells), it makes them resistant to an antibiotic called geneticin.
• Mutant FabI gene (mFabI): This gene comes from a common bacterium called E. coli. It makes the host cell resistant to a chemical called triclosan.