How to Clone Yourself, Part 1: Start Small

In this short series, I explore the modern tools and techniques available to aid you in your (‘diabiological') quest to clone yourself.

It's a dark and stormy night, and you find yourself alone in your basement, cobweb-strewn lab. Wouldn't it be nice to whip up a companion, someone just like you who you can relate to?—A clone of yourself!

Sure, but it's not very likely. Yet sometimes I think that's the image that pops into people's heads when I say that I am cloning as part of my research. When molecular biologists use the term "cloning," they are usually referring to the process of cloning a gene, not an organism. If you want to clone yourself, start small by cloning a gene. You might find something interesting.

Studying a single gene and the protein or proteins it encodes is hampered by the fact that genes exist in a bustling genome. It is often useful to isolate a gene so that it can be studied or manipulated in isolation. For example, cloning the gene for human insulin allows us to produce large amounts of insulin in bacteria.

Cloning is easier than you might think. If you already have a gene in mind you can look it up in a sequenced genome! Let's say you want to clone your insulin gene to see if it's any different from your friend's. In the human genome, the gene for insulin is abbreviated INS and happens to sit on chromosome 11.

The first step is to amplify the gene using a process called PCR, short for polymerase chain reaction. In PCR, short pieces of single-stranded DNA are used as primers to get the reaction going. One primer binds at the front of the gene and the other at the end. Together, they define the region of DNA your PCR reaction will copy, exponentially.

After PCR, you have a tube of DNA that is almost exclusively the INS gene. From here, you can sequence the gene directly by mailing away the INS PCR product (the routine method of DNA sequencing is very similar to PCR, requiring also one of your primers).

But say you are also interested in producing your own supply of insulin, encoded by your own personal INS gene. To do that, you need a cell that can read the instructions encoded in the INS gene to produce functional insulin protein. Luckily, all life on earth uses a shared genetic code and so a gene from one organism can be understood by any other organism. E. coli is usually the first choice, since it grows quickly and is easy to handle.

First you need to figure out a way to get INS into E. coli. The cell needs more instructions than what is encoded in this foreign, human gene, and the DNA needs a vehicle to carry it into the cell.

The solution is to use a plasmid. Plasmids are small, circular molecules of DNA that bacteria faithfully copy before each cell division. The plasmids are easily taken up by bacteria using a simple heat shock procedure, and they stick around because they encode a gene for antibiotic resistance. Growing the bacteria on the corresponding antibiotic means that only the cells with the plasmid can survive.

Here's where the cloning comes in. You insert your INS gene into the plasmid using restriction enzymes. When you transfer the plasmid to E. coli, the cells will produce many copies of the plasmid (and by extension your INS gene) with each cell division. It is this method of precise copying that we call "cloning."

Now, to finish this out you have to instruct the E. coli to express insulin. Though the cells understand the coded message for assembling insulin, they do not have the same machinery as humans to recognize that there is a message to be read! By adding a suitable genetic switch you create what is now called an expression plasmid (or, more commonly, "expression vector.")

As the E. coli cells grow, they faithfully copy your plasmid and express the insulin encoded in your INS gene. With the right biochemical know-how, you can purify this small, cloned part of yourself.

What's truly remarkable about this method of cloning is that you can apply it to any gene you want, although very long genes are tricky to clone.

So now you've cloned a small part of you. In fact, we could say you cloned the smallest unit of you: one gene. In the next post we will look at copying entire cells using technology from the field of stem cells.

Image credit: Madprime (via Wikimedia Commons)