What information is genes telling you? Some people here do not agree that genes actually carry information. My understanding is you are only able to see what the protein makes in the form of bone, tissue etc.
I'm gonna over simplify this for easy clarity.
There has been a concerted effort by geneticists over the last few decades to record all the genes and figure out what they do.
It's easier for us to locate a gene than to determine it's function.
The way you determine function is by looking at a large number of individuals, recording their gene sequences and looking for abnormalities.
If 99% of a population has Gene A, and 1% of that population has Gene B instead, you look at what the Gene B individuals have in common.
Another way to gather this information is to look for odd traits in a population, examine the individual and see what gene variants they have which is not seen in the rest of the population.
A lot of this science is done with fruit flies - largely because they mature quickly and cost almost nothing to keep alive.
Considering that most species do share the same proteins because we share the same parts, wouldn't this make the connection between them harder to determine?
This is why its useful to look for differences.
For example, an albino rat differs from a normal rat in an obvious way. Locating the difference in the code tells us something about the cause of the condition. Then you can compare the gene in the rat where this happened with a gene in a human with a similar condition and see if it's the same error or not.