What is a gene and what does it do?

Genome – it has the word “gene” built into it. But what exactly is a gene? You may remember that the genome is made up of DNA, long strings of bases called A, T, C, and G.  There are certain strings of bases, called a genes, that code for proteins, and proteins are the molecules that do all the stuff in your cells.

Perfectly clear, right?  Of course not, so let’s start with an analogy.  Let’s imagine that one chromosome is a chapter of a book, but the book is written in such a way that the sentences with meaning are mixed in with random letters.  All of the letters are part of the English alphabet, but some of them are written in such a way that they make sense and have meaning – like the sentences written in red below. This is just like your DNA.  Some of the DNA makes readable sentences (genes) and other DNA in between these genes doesn’t (this used to be called junk DNA, but now we know better – more on that later!).

Each of these genes makes a protein (the how of this is a topic for another post).  Let’s give a few examples of genes and proteins that you may be familiar with.  Insulin is a protein that is coded for by the insulin gene. Insulin is important in regulating blood sugar, and people with diabetes often need to inject the insulin protein to help regulate blood sugar.  Another example is the lactase gene.  This gene codes for a protein that makes the enzyme that breaks down lactose.  A decrease in the amount (also known as the “expression”) of the lactase gene is what causes lactose intolerance in adults.

An analogy that is used all of the time is to think of DNA as a blueprint for something – let’s say a car.  Each gene is a blueprint for a different part of the car – a steering wheel, a brake, or a headlight and the protein that each of these individual blueprints make is the steering wheel, brake or headlight itself.  The genome is all of the blueprints put together to make the entire car.  So what does this mean to you?  Imagine if the blueprint for the brake was a little wrong and the brake on your car didn’t work quite right…the car won’t exactly function as intended. It’s the same with genes.  If the gene isn’t quite right, it can make a protein that isn’t quite right, and this can cause the body to not function quite right (causing disease).


And just in case you’re sitting there and still thinking about blueprints and steering wheels and book chapters and codes, let’s summarize how the Genome, DNA, genes, and proteins are all connected in this image here:


3 thoughts on “What is a gene and what does it do?

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