Gene/Chromosome number in evolution.?

Question

First off I'm trying to find a list that compares the average gene sizes and number of genes of humans to other organisms, also chromosome numbers also.

Secondly, in response to the Creationist argument that there is no increase of information, are there mechanisms of information increase? Or is this not a valid argument, i.e. rice having more genes that humans.

Is there some correlation between gene size and number to how complex and organism is?

Thx

Answer 1

Gene number and chromosome number have very little to do with each other. And neither one is a good measure of "information" in a genome, or "complexity" of an organism.

To understand the lack of rel'nship betw. gene number and chromosome number (ploidy), remember that chromosomes are just bits of genetic material ... i.e. the nuclear DNA is just split up into fragments that make replication easier. An organism's DNA can have a lot of genes located on a small number of chromosomes, or a small number of genes located distributed over a large number of chromosomes.

A second point is that the simple *number* of genes can have little correlation to the "complexity" of the organism. A single gene can have multiple complex functions, or affect multiple expressions of other genes ... while a whole collection of genes (some inactive, some active) might together control a rather simple function.

And finally, humans have this bizarre idea that they are somehow more "complex" than all other organisms. Why? We have absolutely no reason to be so conceited. We happen to have big brains. That's it. For example, the digestive system of a ruminant (like a cow or a goat), is far more complex than ours, and may in fact represent far more complexity and a far greater number of genes, than the complexity or genes needed to define our nervous system. Or the details of photosynthesis in rice, or a fern, may be way beyond any complexity (including our brains) in our own bodies.

As far as the response to creationists, I have always been baffled at the "no new information" argument. This can only come from a complete lack of understanding or definition of words like "information" or "complexity."

If "information" means some specific combination that has some effect and gets reproduced, then every single mutation *by definition* is "new information." Sometimes (perhaps most of the time), this "new information" is fatal, and the organism (and thus the mutation) doesn't live very long. Much of the time, this "new information" is neutral (neither harmful nor beneficial) and can thus get passed down for generations until it provides some advantage. And occasionally, this "new information" can be beneficial (even if it actually appeared many generations ago, but the environment has changed), in which case it will propagate more rapidly into the population.

But regardless of whether a mutation is harmful, neutral, or beneficial, in all three cases that mutation is "new information" by any reasonable definition of "information." If the creationist disagrees, then by what definition of "information" is a mutation (even a bad one) not "new information"?

The word "complexity" is even more slippery than "information." But even then, it is a vacant argument to assume that a simple increase in gene number (much less chromosome number) is an increase in "complexity."

That's the problem with these arguments. They throw around words like "information" and "complexity" without any real definition of what they mean. Thus they can make blanket statements like "no new information" or "complexity cannot increase" without actually saying anything of substance. These arguments are intended only to confuse.

Answer 2

you'll find a table of genome sizes and the estimated number of genes in various organisms in the link below. keep in mind that these are estimates and novel genes and pathways of regulation are still being discovered. one of the hot new fields these days is micrornas, which are transcribed off the genome and control the stability of protein-coding rnas, but do not code for protein themselves.

very broadly speaking, the apparent complexity of an organism correlates with the size of its genome and the number of genes. this works when comparing, say, bacteria and yeast to humans and elephants. however, when you get into details it's not very pretty. gene-wise, humans would be estimated to be less complex than mice, and about the same as this small arabidopsis flower. and a very large proprortion of our genes are actually dedicated to our sense of smell. also, it is important not to fall into the idea that organisms today fall into some straight line; we are all parallel branches on the same tree, where some have changed more over time than others. thus i suppose we are "evolved" to the same extent. nevertheless, i think that (and this is more or less subjective) what we do see is that the complexity of gene *regulation* increases dramatically in more complex organisms, in that each new component increases combinatorial complexity a great deal. but i agree with the last answerer -- and so did the judge in the dover trial -- that there are no criteria for what defines complexity, just a subjective sense of it at the extremes.

"lack of information increase" is actually just blatantly false. one human example is that autism seems to give people amazing mental abilities and has increased in incidence over the past few decades. anyway, this "information increase" is supposed to be an argument against, say, humans being evolved from ape-like ancestors. nobody is saying that humans evolved from rice, and as mentioned before, different branches of the tree seem to be growing at different rates and in different ways. you cannot really compare the different branches -- just the organisms along one branch. this issue actually came up during the dover trial in pennsylvania, in related forms called "irreducible complexity" and "purposeful arrangement of parts." these arguments are purposefully structured to ignore the ways in which evolution is known to occur. exaptation is the idea that "new" parts were developed from old parts that got new functions. for instance, the immune system probably developed from a transposase. the bacterial flagellum seems to have developed from a secretory system. the last answerer is also correct in that there are no criteria for what constitutes "new" information. but the creationist argument is about how something like the flagellum could evolve in small steps, rather than just appearing spontaenously from thin air.

Answer 3

I've given a list of references below for the numbers of chromosomes in other organisms. The first has a nice table of the kind you're looking for, the rest give some good info on why there isn't always a direct relationship between gene number and organizational complexity. This should help.