I am trying to understand what exactly a phenotype is to try and understand a ge

Question

I am trying to understand what exactly a phenotype is to try and understand a genetics database. (Ie I don't really know very much about genetics at all)

I've been reading through wikipedia on what a phenotype is and from what I can gather it is an observable trait which may be impacted by a specific gene.

What I would like to know is if you were looking for the presence of a phenotype such as red hair, would characteristics like not red hair and carrier of red hair also be phenotypes?

For example the following table is named Phenotype,

+------+------------------+
| Code | Description |
+------+------------------+
| RR | Red Hair | this makes sense with my understanding of phenotype
| RN | Red Hair Carrier | this doesnt
| NR | Red Hair Carrier | this doesnt
| NN | No Red Hair | this doesnt
+------+------------------+

The whole code column looks like it represents a gene not a phenotype

Explanation / Answer

"I think this comes down to whether you include being a carrier of a genetic "condition" a part of your phenotype. It's almost a question of semantics"

To expand on this, I would say there are two major definitions of phenotype, and both are employed by geneticists depending on the context. Definition one is a bit more naive, and I tend to use it when teaching or trying to explain phenotype to a layman: anything you can observe is a phenotype. Under this definition, having red hair is a phenotype, not having red hair (or, more directly, having black, brown, blonde, etc. hair) is a phenotype, but carrying the recessive gene for red hair is not a phenotype. I can observe without checking your genome that you do or don't have red hair, I cannot tell without checking your genome that you have one copy of the recessive gene for red hair.

Definition two is more complete, and I tend to use it more in a lab research setting: anything that is the OUTCOME of a genotype can be defined as a phenotype. Again, red hair and not red hair (meaning brown, black, blonde, etc) are outcomes defined by the genotype. However, depending on the context (let's say I'm interested in understanding heritable potential and not the color of hair) I'd say that the phenotypes would be 1) the ability to pass on red hair to progeny (outcomes of genotypes RR, RN, RN in your example), and 2) lack of ability to pass on red hair to progeny (outcome of genotype NN in your example). In both cases, the phenotype is the outcome of the underlying genes, I just have to make sure I frame my scientific context appropriately.

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