The P generation is where all the crossing starts. It is the purebred generation and those dogs are accepted and registered as pure dogs in different kennel clubs. This group includes all the breeds such German Shepherd, French Bulldog, Pug, Golden Retriever or Chihuahua.
When someone decides to create a new type of a dog, he will cross two purebred dogs together in order to create a new crossbreed, thus, he will be creating the first generation cross, also known as F1 cross. Sometimes, crossbreeds are also called as designer dog breeds, but it means the exact same thing → an offspring of two purebred dogs.
The F1 crossbreeds inherit 50% of genes from breed A and 50% of genes from breed B. The appearance and temperament of the F1 crosses is the most unpredictable as they can inherit traits from both parents equally.
But the breeders want to achieve some kind of dreamed appearance and temperament, for which they started the crossing. And because of that, they are breeding further the offsprings with the desired appearance and temperament.
And when they breed two F1 crosses together, they are creating second generation crosses, or F2 crosses. And when you breed two F2 crosses, you are creating third generation crosses, also known as F3 crosses.
I am sure you got this. You can also have F4, F5, F6 crosses and so on. But to make it simplier, any generation that is higher than F3 is typically called as multi generation.
It is important to say, that F3 cross does not need to be offspring of two F2 dogs, but also an offspring of two F1b crosses. But what does that mean? What is the F1b and F2b?
Well, the little b stands for „back cross“. It is a result of mating F1 cross back to the purebred parent. I can show you an example on one of the most popular crossbreed, the Goldendoodle.
One of the most desired characteristic of Goldendoodle is their almost non shedding coat. It is a trait inherited from the Poodle parent. And to make it more likely that the Goldendoodle will truly have the low shedding coat, it is better to increase the percentage of the Poodle in the cross.
That can be easily done by outcrossing the first generation Goldendoodle back to the Poodle. The result is F1b Goldendoodle which is 75% Poodle and 25% Golden Retriever.
F2b generation is also a back cross, but in this case, it is a result of mating second generation cross with the purebred parent.
So as you can see, understanding the generations is not that hard as it might seem. It is also important to say, that it is not essential to understand the generations. More important than that is to choose a breeder with good reputation. This breeder should answer you all the questions and help you to get you a dog with the temperament, appearance, size and coat you want.
But remember, all the crosses, no matter what generation it is, are still quite unpredictable in terms of appearance and temperament, much more than purebred dogs.