dna

[kwicky]

You often hear of other species containing some percentage of human DNA. ie a chimp has 99%. Are all living creatures genes a sub section of human DNA?

I suppose what I am getting at is if we came from the apes extra genes were added. But alternatively was the original blueprint the human DNA and genes were removed to create other species.

[brachiopod]

I've heard some really mangled interpretations of evolutionary theory in my time, the hackneyed one being "man descended from the apes" (that we share a common ancestor would probably be more accurate)

I've never before heard that "animals are derived from man" though !!

Once again, human arrogance (the human-centric approach) assumes that we are at the centre of it all - either as the "end result", the ultimate 'purpose' of evolution, or - (and to be honest, haven't heard this argument before - even from any religion) - that all species are derived from humans (or human DNA).

[kwicky]

Many theories were put forward about evolution before the discovery of DNA. Some even proposed we evolved from the fish. Others said we derived from apes. All from conjecture.
Now we have some minute evidence in the form of DNA and genes. We can differentiate between different species by the genetic footprint. All species have to some extent identical genes to humans.
Without bringing religion or evolution or pre conceived ideasinto it by just studying the genetic code we are more likely to reach a better conclusion. Rule nothing out or in!

[kwicky]

Using DNA to spot differences between a chimp and a human without consulting evolution or religious studies.

http://www.discover.com/issues/apr-06/features /chimp-genome/

[honest_joe]

The article from that neuroscientist who has studied the differences between chimp and human DNA tells us a great deal. Human brain cells have reached a stage of intelligence where they divide exponentially but a switch turns off the process at a certain level. If this switch was turned off later more brain cells would be made and an exceptional human with greater intelligence would result.
The difference between that of a chimp is that switch off occurs earlier. The switch is a particular gene and who is to say when we are modifiying genes what senario we are moving to.

[kwicky]

Yes the article was very clear. I was not aware that genes of the animal kingdom and humans were often identical but depended on a switch just before the gene which turned it on. The remarkable thing was that the promoter that controlled the switch had a multi action role just as turning on the light switch in a room will turn all the bulbs on not just one.

[chakka35]

It's not a good idea, kwicky, to bracket evolution and religion together like that. The science of evolution is central to the matters you are discussing; religion makes no contribution. I suggest you read Richard Dawkins' stunning book "The Ancestor's Tale" which explains it all lucidly and graphically.
By the way, not only are we not descended from apes but we are apes. (I wish I could do italics in AB. Does anyone now how?) The Great Apes are humans, chimpanzees, bonobos, gorillas and orang-utans.

[kwicky]

Chakka I am leaving evolution and religion out of the discussion and concentrating on genetics.
Have you heard of Fred Sanger (Cambridge). He was awarded 2 nobel prizes in genetics. You should study his work!
His 2nd Nobel Prize was for decoding the virus IX174. This virus had eight genes in total. It was established that ATG is the start sequence of a gene. The number of nucleotides was about 5000 and the code was in triplets. The beauty of this virus was that some genes overlapped by changing the reading frame so you had a gene within a gene. It was a pleasure to see genetics in the raw at such a low level. The I in IX174 should be Phi but I dont know how to produce the symbol.

[jake-the-peg]

I think the exact mechanism of DNA coding and evolution is probably a fair bit more complex.

Take the so called C-value enigma http://en.wikipedia.org/wiki/C-value_paradox

The size of the genome does not necessarily match the complexity of an organism.

For example there's an african Lungfish with a genome size 132pg compared to our measley 3.5.

Up to 97% of our DNA seems to have no purpose so called Junk DNA.

It would apppear that evolution may be slowly optimising the size of DNA in species as well.

[kwicky]

Jake I take note of your answer regarding quanity of DNA but disagree with your comment about junk DNA. This was the original hypothesis but now the conclusion it is not junk. The higher the organism the greater the need for intensive examination that is why I quoted a virus above with just 8 genes. At the time scientists said that the coding for the non gene area was junk. My suspicion is that a functioning program (just like a computer program) is contained within it. I thought at the time you could convert genes into proteins but how are the number of spikes formed on the casing (I believe there were about 8) without an iterative process.

[kwicky]

Junk DNA - the jury is still out on this. The discoverer will surely be in line for the next Nobel prize.

http://en.wikipedia.org/wiki/Junk_DNA

[jake-the-peg]

Well I did say "so called".

There is a tendency to believe that organisms are so finely tuned that if there are constituents that have no observable purpose it must be because we do not yet understand it.

I think this is circular logic - we see evidence that organisms are not as finely tuned as we thought so assume it must be because we do not fully understand it.

Of course as you brought up the subject of computer programs, you will find if you examine one with a hex editor, large areas of blank space which is unused, a quirk of the compiler.

If large areas of DNA are unused for any reason, there is no immediately obvious (at least to me) reason why they would be a major evolutionary disadvantage, or atleast not a major one.

I'd suggest it's quite conceivable that inefficiencies in genetic encoding could continue to be passed down over the generations.

Proving it of course is entirely another matter, Proving a negative is notoriously difficult.

[brachiopod]

"All species have, to some extent, identical genes to humans"

The cheating, copying ********!!! Still, amoeboids must be really stupid, since they only managed to copy about 92% of a human's genetic make-up.....

[brachiopod]

****** = (en Francais), b�tard (n.)

[kwicky]

Brachiopods 1st answer is nearer the mark. Looking at that article in the 3rd reply above with a common ancesty betweens chimps and human seems to be quite logical. Because all genes are not switched on by having a general gene pool they can be selected either to create a human or a chimp.

[kwicky]

It is misleading to say that a chimp has 98% of human DNA. It seems that the important part is the switch that triggers an array of genes and there are millions of these.

[kwicky]

There is much discsussion between the species and ancestry. For greater factual detail this article would explain it more accurately.

http://www.ncbi.nlm.nih.gov/About/primer/bioin formatics.html