UNDER THE MICROSCOPE: WHAT ARE DNA, RNA, AND PROTEINS?

What are DNA, RNA, and proteins? “Well, that’s easy,” you may be thinking. “DNA is made from four bases, is in the shape of a right-handed double helix, and is the basis for everything within our cells. It is broken down into units called genes, which are translated into mRNA before being transcribed into proteins.”

Fun Fact: DNA is an initialism, not an acronym. Acronyms are for abbreviations that are words, like NASA and SCUBA. Initialisms are for things that are initials, such as FBI, DoD, and, of course, DNA.

But how do you describe DNA to someone without a scientific background? Perhaps not so easy. Over to Dr Michael Weiner who will help you with this task.

Photo by Patrick Tomasso

Start by imagining two rooms. In the first room is a 1-million page instruction manual for every ‘thing’ you would ever need to make a human being. That manual rarely changes and can never leave the first room.

In the second room, there is a carpenter who can build any ‘thing’ at all. But only if given precise instructions from the instruction manual in the first room. Note that the instruction manual in the first room describes how to build the ‘thing’. It’s not the ‘thing’ itself. For example, if the instructions describe how to build a birdhouse, the birdhouse is the ‘thing’ the carpenter builds. The instructions are just words on a piece of paper. Just words. In detail.

What the carpenter is doing is translating the instructions from words on a piece of paper into something entirely different. In the everyday world, ‘translation’ means changing something written or spoken in one language into another language, and that meaning is no different in biology.

Photo by Brandon Kaida

So how do you get the instructions from the million-page instruction manual to the carpenter? Easy, let’s hire a messenger who will perform the following:

1. Go into the first room.
2. Lookup the ‘thing’ that needs to get built,
3. Write down the instructions on how to build that ‘thing’ on a piece of paper.
4. Go into the second room and hand the instructions to the carpenter. And now, with these instructions, the carpenter will make the ‘thing’.

The million-page instruction manual stayed in the first room. The carpenter stayed in the second room. The messenger carried the information between the two rooms.

Now, in this case, the messenger is taking the instructions from the book in the first room and transcribing them onto a piece of paper. The messenger didn’t translate the instructions from one language to another but merely transcribed them from one format (a book) to another format (a sheet of paper).

But what if you want to make tens, hundreds, or even thousands of the same ‘thing’? You can either:

1. Have the messenger go back and forth that number of times, rewriting the instructions each time, or
2. Once the carpenter has finished building the thing, take the piece of paper from that carpenter and hand it to them, again.

Both methods end up at the same result: a multitude of copies of the same ‘thing’. You may note that the second way will be much faster, but speed and efficiency are not always the best. For example, rushing through a 5-star dining experience at the same frantic pace as you would at a fast-food drive-in does not make the 5-star dining experience ‘better’.

Photo by Hans Reniers

As scientists, you will have realized that DNA is the instruction manual in the first room (which is itself the nucleus of the cell) and the messenger is RNA, or, to be more specific, messenger RNA (mRNA). The mRNA takes the instruction to the correct machinery to be made into a ‘thing’, or protein.

Fun Fact: The human genome is composed of 3 billion ‘letters’, which is equivalent to 1 million pages, or 2,500 average books. If DNA was the width of a piece of paper (8.5 inches), then it’s length would be 24,000 miles: equal to once around the Earth at the equator and over 100 hundred million times longer than it is wide!

In the introduction to this series, I mentioned that science had been flung into everyone’s homes due to COVID-19. So, how does this article help you explain the COVID-19 virus, SARS-CoV-2?

SARS-CoV-2 is an RNA virus. In other words, it is all message. When it invades, it enters the second room and stays in the second room. It never goes into the first room, it is never DNA, it is never an instruction manual.

In the second room, it hogs the carpenter’s time. Every time the carpenter completes a ‘thing’, SARS-CoV-2 jumps the line in front of any other messenger coming out of the first room and demands the carpenter make more SARS-CoV-2 ‘things’ first. This is what we mean when we say the virus is ‘taking over the cell’s machinery’.

The cell is now making SARS-CoV-2 ‘things’ and is no longer making the things that the cell needs to keep living. This is not sustainable for the cell and eventually results in cell death. As the cell dies, it ruptures, and multiple copies of SARS-CoV-2 are released from the cell; it’s like rats abandoning a sinking ship. Only in this case, the rats also made the ship sink.

In the next part of this series, we will focus on how to explain a familiar technique to scientists, the polymerase chain reaction (PCR).

About Dr Michael Weiner

Dr Michael Weiner is Abcam’s Vice President of Molecular Sciences. Throughout his career he has founded more than four biotech companies, including Affomix, GnuBio, and AxioMx.

Throughout his career, Dr Weiner has developed several tools widely used in molecular biology. These include the first commercial Next Generation DNA sequencing instrument, a bead-based genotyping method, and improved methods for the production of monoclonal antibodies.

Beyond his career as a scientist, Dr Weiner is a dedicated mentor to multiple bioscience professionals. He is also an inventive artist!