For a very entertaining and educational book that tangentially related; I can highly recommend: Y - The Descent of Man by Steve Jones [0]
I am thrilled to see more chromosomes being mapped/sequenced. Please excuse my high-school level of biology knowledge here, but have we definitively progressed beyond correlation when it comes to genes, gene expression, and how they all interact?
Take "Blue eyes" as an example, we know that [1] OCA2 is responsible for brown/blue eye colour. BUT are we sure that none of the 20,000 others are involved/needed?
In laymans terms I would guess that to get 'blue eyes' would require several genes to ALL be on/active/present as well. More like a recipe, then a simple on/off it's located in 1 position.
Eye color is subtle. How do you define blue eyes? It's not just one phenotype; there are a range of blue eyes, whose differences correspond to fairly subtle variations between people. The article you linked [1], is quite good but requires quite some time to absorb completely.
I would imagine all sorts of genes are necessary to have blue eyes depending on how you look at it. After all, you need eyes in order to have blue eyes, and a whole bunch of other machinery to open them to check the color...
First I would like to state that human genetics are very, very complex and we still do not have a complete understanding of them. For example, only relatively recently has the field of epigenetics made major advancementa, which (broadly speaking) studies how a cell's behavior can be changed WITHOUT it's DNA being changed.[1] This brings into question the age-old questions about environmental impact vs genetic impact in even greater detail. Anyways, sidebar over.
No, we are not completely sure how many chromosomes play a role in determining eye color. However, we do have a pretty good guess. Most recent estimates I found out the number at 16. OCA2 and HERC2 have the largest impact on eye color, but, there are many OTHER genes that also have smaller impacts on eye color. [2] That article I cited is actually amazing. But, it does touch on some more advanced subjects that are more introductory college-level biology or AP Biology than standard high school bio e.g. Gene Regulation, introns and extrons, etc.
To answer your more general question, in my (admittedly only mildly less basic, introductory college-level biology) opinion, it is unlikely that we will, anytime soon, reach a point where anything in genetics can be completly, 100% definitive.
This is not to say that we haven't made amazing advancements in the field of genetics and biology more broadly. BUT, it would be a mistake to take for granted the complexity of the human genome. There is most definitely things we still do not understand about the genome, and will not for some time.
But, practically speaking, while other genes may have impact on some simple phenotypic traits, such as eye color, we can generally make an accurate guess based on only a few genes. In eye color, for example, one study was able to predict eye color with only 6 genes with about ~75% accuracy. [3]
The crazy part is, sometimes the genes that effect the phenotypic trait, don't actually store genetic material that determines the trait. In other words, they don't DIRECTLY determine the trait at all. Rather, the only effect ORHER genes which then effect the expression of the trait more directly. You can imagine that this could become very complex very very quickly when you have multiple genes effecting other genes which effect other genes, not to mention accoubting for environmental and demographic baises when doing these studies and you begin to see why this genetics is such a difficult field of study.
Apologies for the long post and rambling. Hopefully I was still able to provide you with some mediocre introductory-collage-level biology
I am thrilled to see more chromosomes being mapped/sequenced. Please excuse my high-school level of biology knowledge here, but have we definitively progressed beyond correlation when it comes to genes, gene expression, and how they all interact?
Take "Blue eyes" as an example, we know that [1] OCA2 is responsible for brown/blue eye colour. BUT are we sure that none of the 20,000 others are involved/needed?
In laymans terms I would guess that to get 'blue eyes' would require several genes to ALL be on/active/present as well. More like a recipe, then a simple on/off it's located in 1 position.
[0] https://www.goodreads.com/work/editions/436071-y-the-descent... [1] https://www.nature.com/articles/s41433-021-01749-x