Wrong use of genetic nomenclature in "breeding-back"

I have noticed that a lot of genetic terms have been kind of misused in “breeding-back”, and I was guilty of that myself in the past. It should always be paid attention that technical terms are used in the true conventional meaning of the word. In this post I give a little overview over the terms that I have noticed to have been used wrongly (and I used wrongly myself in the past). 

Phenotype: While “genotype” is quite clear, there might be a misunderstanding of what a phenotype actually is. A phenotype is not just the looks or the physical morphology of the animal, but every factual aspect of the living organism – its morphology, its physiology, its behaviour et cetera. So when you talk about a bull with a “good/suitable phenotype” you are also talking about its behaviour and all other aspects. The phenotype is not only influenced by the genotype alone but also environmental and epigenetic factors, and the interesting thing is that there is mutual influence between those factors. 

Ecotype: Not everything is an ecotype. An ecotype refers to a variant, population or subspecies of a species that differs from the others primarily in ecological respects. Most ecotype examples are found in plants, and not so many in animals (Wikipedia, for example, lists only a few whale species). One could say domestic animals are “ecotypes” of their wildtypes, but they also differ fundamentally in morphology, behaviour and genetics and not only ecology, that is why they are classified as different subspecies/populations/species and not ecotypes. 

Gene/allele: Not everything is caused by a particular “gene” or “allele”. Many times traits are multifactorial and caused by a number of genes, and very often a trait is just influenced by pleiotropic effects, development and phenotypic plasticity. For example, I can say with 100% certainty that there is no “allele for long snouts” or “allele for robustness” et cetera. Using a very technical language but at the same time exposing a rather simplistic conception of how an organism comes to shape is slightly absurd. 

P, F1, F2, F3….: The filial generation terminology is actually only used for a strict scheme of crossing: two animals of a different genotype, the P(arental)generation, are crossed with each other, the result is called F(ilial)1individual. Two F1 individuals produce an F2 individual and so on. When an F1 individual is crossed with an individual of the P genotype, it is called a B(ack-cross)1individual. The F-terminology is used commonly in “breeding-back”, but not always correctly. For example, Lamarck – a cross between a pure Sayaguesa cow and a Heck x Chianina bull – is a second-generation crossbreed, but not an F2 because its parents are of a different genotype. It is not a back-cross either because Sayaguesa is a third genotype beside Chianina and Heck of the parental generation. Actually, if you want to apply the F-terminology forcefully here, it is an F1, a cross of genotype A (Sayaugesa) and genotype B (Heck x Chianina). Its son Londo, a third-generation bull, was a true F2 as its parents were of the same genotype. This is where it gets confusing, which is why I do not use the F-terminology for “breeding-back” results anymore. 

Back-crossing: this concept is explained above and should not be confused with “back-breeding” or “breeding-back”.