Question about evolution?

Question

Through the evolutionary process how does information increase on the genome? Or in other words how can point mutations create new chromosomes or lengthen a strand of DNA? I.e. mice have 20 chromosones , humans have 23 and dogs have 39. How can genetic mutations create new chromosones?


I doubt that anyone can give me a satisfactory answer (but if you can provide a link) because this is one of the holes in the theory. And no this is not creationists propaganda, but a genuine question about the theory.

Answer 1

Your first paragraph is a great question!

But your second paragraph is odd. You declare quite decisively that it is "one of the holes in the theory" without waiting to see if someone actually has an answer! If there were a hole so glaringly huge, don't you think scientists would have considered it? Scientists are not total idiots.

A course in genetics 101 will answer these questions rather easily.

The "information increase" question is often asked without giving a definition of what the asker *means* by "information increase." However, you were kind enough to indicate that you think the amount of information is related to the number of chromosomes.

But this just isn't true. (Looking at the total number of chromosomes here:) Humans have 46 chromosomes. A dog has 78 chromosomes. Algae have 148 chromosomes. A fern has 1260 chromosomes. And aulacantha (a single-celled protozoan) has a whopping 1600 chromosomes(!) But this does not mean that they have "more information" than humans do.

The number of chromosomes just means that the DNA of the organism is broken up into more pieces. (I.e. just breaking a cookie into multiple pieces does not "increase information.")

Second, why do you limit mutations to "point mutations"?

Point mutations are just one of *many* kinds of mutations. A point mutation is just a substitution of one nucleotide for another. But there are also translocations, gene duplications, deletions, insertions, gene inversions, chromosome fusions, etc. etc. Many of these can lengthen a strand of DNA, or shorten it, or split it into two pieces, or fuse two chromosomes together.

For example, a chromosome fusion is caused by a runaway translocation error. During replication, it is not uncommon for part of a chromosome to be copied to a different part of the same chromosome, or even to a different chromosome ... what's called a 'translocation'. In some cases this translocation can copy the entire contents of one cromosome onto the end of another ... effectively fusing the two chromosomes.

This is what we believe happened in the branch that led to Homo sapiens (after the split from the apes) and why humans have 23 pairs of chromosomes while other apes have 24. We can see evidence of a chromosome fusion because the genes line up ... nucleotide-for-nucleotide ... between our chromosome 2, and two chimp chromosomes (see source).

As for what can cause an *increase* in the number of chromosome number, there are two mechanisms ... polyploidy, and chromosome fission. Polyploidy is where a normal chromosome duplication occurs during replication, but is interrupted before the cell splits, resulting in an extra copy of the entire chromosome, or the entire *genome* of the organism. This is how haploid organisms became diploid, and diploid organisms became tetraploid (mostly in plants). And other numbers can be produced by hybridization ... for example, a tetraploid watermelon hybridized with a diploid watermelon produces a triploid watermelon ... which is the seedless watermelon we buy in stores.

Chromosome fission (splitting of a chromosome) is more rare than chromosome fusion (joining of two chromosomes), but is observed in fruit flies, and seems to be the source of microchromosomes (tiny chromosomes without much useful genes) found in birds.

Third, and finally, all of these types of mutations can work in tandem. For example a gene duplication can produce a second, redundant copy of a gene that codes for some protein (which also lengthens the strand of DNA). And then ... perhaps *many* generations later ... a point mutation on one of those copies can change its properties so that it is no longer an exact duplicate, but a protein with slightly different properties. So the result is that what was once one gene for one protein ... is now two genes that code for two slightly different proteins.

There is considerable evidence that this is exactly why humans (and the other apes and Old World monkeys, but not New World primates) have three-color vision ... a gene duplication of the opsin gene that produces the protein in the retina that responds to medium-wavelength light ... followed by a point mutation on one of those copies that changed its wavelength sensitivity to produce a long-wavelength protein. So our two-color vision became three-color vision. Two proteins became three proteins.

... That's an "information increase" by *any* definition of what "information increase" means.

In short, genetics has *far* more things going on than simple "point mutations."

Answer 2

1. Strand breaks and failure of the repair machinery
2. Germline cell mutations/fault in replication where chromsomes don't segregate properly. this sort of stuff leads to well documented diseases like Down's syndrome.
3. Mutations in 1 of a pair of chromosomes to such a state that they can no longer pair up during mitosis and both copies get allocated into the same daughter cell. Thought to be how the Y chromosome came about (current thinking says that millions of years ago the X and Y chromsomes were actually the same ones).

Just because you dont know the answer doesn't mean nobody else has an explaination... It really depends on how much genetics you know/understand. Would be happy to point you toward some papers if you want.

oh sorry forgot about the first part of the question, information increases; like with all things errors accumulate over time (i.e. you type 100words 1 may be mispelt, you type 1000 and that may become 10) and there is no reason for the cell/organism to get rid of non lethal mutations. These can just be duplicates of genes which then go on to mutate to such a stage where it fulfils a different function; note the globin family of genes. A lot of the DNA in thought to be just that, random mutations (insertions, translocations, duplications, inversions) which has no meaning and until a selective pressure is applied onto the genome/organism and a considerable amount of eukaryotic DNA is actually retroviral; i.e. from dead retroviruses.

Like i said, if you are genuinely interest and have a basic understanding i could point you toward some texts/papers.

Answer 3

DNA can mutate in many different ways besides point mutations. Transposons duplicate DNA. Those duplicated sequences can contain parts of genes. Those new stretches can mutate randomly to become new genes. Chromosome number can be increased by chromosome doubling. Mutations such are inversions of stretches of DNA can also result in gametes with changed chromosome number.

"I doubt that anyone can give me a satisfactory answer (but if you can provide a link) because this is one of the holes in the theory."

First learn genetics, then look for holes in the theory. You aren't ready yet. My final link is a an abstract of a scholarly study of this question. Did you really think that all genetics researchers just glossed over the question of chromosome evolution?

Answer 4

Primarily gene duplication; also chromosome duplication (ever hear of trisomy-21, aka Down's syndrome?). Polyploidy is specific to plants - modern tetraploid corn is a beautiful example.

So, no, it's not a hole. But good question to ask, I used to think it was a hole too.

Eh, good old wikipedia already has some good starting sources, so I'll point you there. Check out the references on the articles if you want more.

Answer 5

a million) in accordance to evolutionists, people progressed from apes? people are apes by way of definition. Linnaeus categorised us as such and he became a creationist. 2) there are various shown information in technological know-how, yet evolution is basically a concept. fake as a results of a pretend impression of the notice concept. A fact, in technological know-how, is a discrete factor of suggestions. Theories connect information and clarify them. there is no bigger type than concept. 3) A transitional type is a fossil of an animal it somewhat is section one species and section yet another. fake. All organisms are transitional. 4) The age of the earth is desperate by way of scientists totally during the radioactive relationship of fossils ? The age of the Earth became desperate by way of relationship a meteor on the concept that the image voltaic equipment became each and every of an analogous age. All different calculations greater healthful the age got here across. 5) The medical approach starts off with a prediction and then looks for evidence to help that prediction? It starts off with remark. Then a hypothesis is formed from that remark. After the hypothesis is formed, scientists seek for evidence to help or falsify the hypothesis. 6) the thought of evolution includes the great Bang? fake. 7) To have faith in evolution is to have faith that existence and remember got here from no longer something? fake.

Answer 6

The size of the genome or number of chromosomes has little to do with complexity of the creature. You have arranged a list in ascending order of complexity (presumably), but fruit flies have 4 and yeast has 16.

Answer 7

http://en.allexperts.com/z/js/o.htm?k=dna%20genetics&d=DNA%20Genetics&r=http%3A//en.allexperts.com/q/Genetics-1795/extra-pair-chromosones.htm