Genetic Similarities

I'm curious about genetic similarities between all life on earth (including plants and animals). For me one of the most convincing reasons to believe in evolution would be similarities in the genetic code of animals that currently look similar, and as similarity decreased, so would the genetic code. This is explained by evolution because from a common ancestor, genetic mutations would become different over time. Most of the differences would occur in DNA that wasn't essential to the survival of the species (it's easier to tinker with non-essential aspects of a system).Essential systems, however, over time should remain relatively constant. I remember reading somewhere (i can't remember exactly) that cows and pea plants (including all other life on earth) share a common sequence of DNA that codes for the splitting of mitochondria.I'm almost positive my above example is wrong in some way, so i was wondering if someone could correct my example. Is there a sequence of DNA that is found in most (if not all) life on earth that codes for a specific process that we know about?Creationists talk about how no matter how many times dogs have offspring, the offspring will always be dogs. They also comment that regardless of how similar the genetic code between chimps and humans are different "kinds". my second question is what are the respective genetic differences between very dissimilar dogs (lets say st. bernards and chihuahuas... but i'll take anything really) and chimps and humans?I think creationists would predict the genetic differences in dogs (the same kind) would be LESS than the genetic differences in chimps and humans (different kinds).unless they see no correlation at all between genetic code and kinds... but i would still like to know the answer.[This message has been edited by TheoMorphic, 10-28-2003]

i'm looking more for a specific example. is there an essential sequence of genetic material that all (or most) life has in common (maybe not exactly the same, but significantly similar)? does this sequence code for something so essential that a minor change does not allow the organism to develop into reproductive maturity?

holy crap dude... that was over on the brad mcfall side of the incomprehensibility scale.by example i mean "So there is a sequence of DNA that codes for Operation X. Every organism on earth has to perform Operation X at some point in their life. Humans have this sequence that codes for Operation X, and so does this boot scum that i found in my closet (on my boot)."call me lazy (in that I would prefer to not have to do extensive research in biochemistry and genetics to understand the example) but understanding calculus (actually understanding it, not just going through the motions) is taking up enough of my time right now.