Genes: most people have probably heard of them before, maybe in a biology class many years ago, in a news article about some discovery or possibly even the doctor's office. But what is a gene exactly, and what does it do?
Genes: the building blocks of life
A gene is a small piece of DNA that contains the information for a specific trait. Each gene has the instructions to build certain proteins. In turn, these proteins support nearly everything our body does. From antibodies and hormones to building muscles and pigments that determine coat color: they all rely on these proteins!
Outside of these protein-coding genes, there are also sections of DNA that don't make any proteins at all. This "non-coding DNA" often still has a function, though. It can, for example, regulate other genes and turn them on or off.
You can think of a gene as a recipe for a specific dish. Small changes in the recipe can dramatically change the final result. If a certain ingredient is missing or replaced with something else, the dish might not be tasty anymore. A family recipe that is passed down over generations might build up small differences over time. If no cook is present to start making the dish, then nothing will happen at all. These are all things that could happen to our genes as well, causing variation between individuals.
Chromosomes
If genes are like recipes, then chromosomes are like cookbooks. Chromosomes are long strands of DNA, tightly packed together so that they fit into our tiny cells. If we were to stretch it out, the DNA of one of our cells would be 2m long! All genes are organised on these chromosomes.
Chromosomes come in pairs. Horses have 32 pairs, or 64 chromosomes in total, in every cell. This means that we have two versions of each chromosome and, consequently, of each gene (except for the sex chromosomes). However, even though we always have two genes that contain the recipe for the same dish, the recipes can be slightly different between them.
One chromosome of each pair is passed on to the offspring. Each horse inherits one chromosome from its sire (father) and one from its dam (mother), making it a unique blend of both parents.
