Propblem:

I was recently reading about colinearity in the HOX genes that give an organism its high-level body plan (where the order of the HOX genes on the chromosome follow the head-to-tail order of body segments, such that the head gene comes before the thorax gene, comes before the abdomen gene, etc).

I'm really just an interested laymen with this stuff (only completed A & P I). But I was under the impression that the location of genes on a chromosome has no bearing on the expression of those genes or phenotype of the organism, that genes can be anywhere on any chromosome.

Required:

Question: Do we understand how the order of the HOX genes ends up being expressed as the order of the body segments?

Question: Do we know why the positioning of these genes matter when the order of other genes don't?

Explain your reasoning of your answer.