1) I understand different species have different number of chromosomes but what do these numbers actually represent? i.e. What is the significance of Humans and hares having both 46 chromosomes?

2) If we found the DNA of, say, Isaac Newton and since thats the code that includes every instruction to build him, would it be possible to make a clone of him with current technology? With hypothetical technology?

3) How long does it take for the environment to mutate genes so it better adapts to it? Such as some people having light skin due to lack of sunlight in those areas necessary for Vitamin D production. How does the mutation "know" which gene to alter so that the skin becomes brighter?

4) Doesn't the "few billion" bits of data that the human DNA stores seem a bit too low? I would imagine there would be way more data on how a human would function. All those cells would need a lot of instructions.

I will post more questions when I remember those that I was thinking on before.

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A slight inclination of the cranium is as adequate as a spasmodic movement of one optic towards an equinine quadruped utterly devoid of any visionary capacity.

try posting the questions on the talk.origins usenet group, you will get specialists in the field answering, also check out the www.talkorigins.org website

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Is talkorigins the one with the great pages on Piltdown Man?

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I want to go back to the moon.
I don't care which rocket you use, whichever one you pick, I'll like it, I swear.
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek

It has no known significance. It's just how many chunks the total nuclear DNA is broken up into, with no known effects on phenotype. It could be random.

Current technology can't clone any human under any circumstances, or any primate for that matter, or even most other mammals. But the fact that it's been done with a few mammals is widely taken by geneticists as an indication that it is something they can figure out how to do, not something the laws of nature somehow preclude. It's generally seen as a matter of when, not if.

There is no set rate of mutation or of selection. Both are different in different cases. For example, human body size and proportions seem to change more quickly than human skin color. But mutations do not at all know what changes to make. They just happen by accident, and then either turn out to be benecifical or not. Many mutations go in the wrong direction or go too far, but those mutations don't become very common in the population.

It takes more data to fully describe a human body, or even just the brain alone, than DNA can contain. But the DNA doesn't need to contain every single detail about you. A lot of the details will instead come from interactions of your cells with each other and with the outside environment, or are just redundant copies made from a single original stored piece of information.

Nothing. Only that human and hare DNA is splitted in as many parts.

With current technology that is impossible. I guess that by replacing the DNA in a zygote with his a clone might be produced. In reality however that would be impossible even if we had some well-preserved tissue samples. DNA doesn't survive for centuries and it would be useless. Not to mention revived mammoths or dinosaurs.

Mutation is practically a random process. It absolutely doesn't "know" anything. Vast majority of mutations are irrelevant or even harmful (like genetic diseases for example), but a very few actually increase the fitness of an individual. Such individuals succeed better at reproduction (more of them stay alive long enough to get offspring, or they're more sexually attractive etc.) and the relatively number of offspring carrying that mutation increase in the population.

It has been speculated that the lighter skin may be related to the domestication of cattle in Eurasia; people got the required vitamin D from milk (and developed lactose tolerance in the process; imagine how huge advantage it was to be able to drink cow milk after infancy). In addition, it didn't matter if darker skin "degenerated" as humans at higher latitudes didn't need so good protection against skin cancer.

The DNA is much more than a sequence of nucleic acids. Although chimps and us share almost identical DNA, the crucial difference lies in how different genes are active. In order to truly understand an organism, one has to know how its genes operate. DNA sequencing is needed, but it is far from enough.

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Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

DNA is not uniqely describable by a sequence of nucleic acids? And where does the information come from that determines how its genes operate?

I thought of the issue of DNA degradation but forgot to mention it. I'm not sure DNA from Newton's time couldn't have been preserved intact to the present; even Neanderthal DNA in some cases remains intact enough to have been tested and found quite distinct from human DNA. However, preserving it even from Newton's time would require the right circumstances, creating an environment in which DNA degrades slowly... and I believe they just buried him as usual rather than putting any effort into any attempts to preserve him.

This is not accurate. Lactose tolerance is much more common in human lineages with a long history of dairy animal use, such as white people (although not exclusively them) but that has nothing to do with vitamin D, sunlight, or even skin color. Human skin produces vitamin D upon exposure to sunlight, and lighter skin is better at it, but that has nothing to do with milk consumption. (You might be thinking of the label on some milk containers, "vitamin D milk", but what that means is that vitamin D has been added to it as a dietary supplement... an ironic choice of food to put it in, because the people who need such supplements the most are also the least likely to consume milk, but that's what's being done. Natural milk is not a significant source of vitamin D.)

Thanks for the answers.

5) I have heard some genes are only given to you by your mother and others exclusively by your father. Is this true? Which genes are actually contained in the X and Y chromosomes and does that mean certain genes are more like to be inherited from a particular parent? i.e sons more likely to get the height gene from mothers, daughters from fathers

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A slight inclination of the cranium is as adequate as a spasmodic movement of one optic towards an equinine quadruped utterly devoid of any visionary capacity.

Um, my point was to downplay the usual "organism x has n % of our genes" claims. All information needed is of course coded into DNA, but by simply comparing different sequences one can't say how genes operate. Same genes activate differently in different organisms and so on. That's why we're so different despite that our DNA looks so similar. Therefore, "DNA is more than the sum of its nucleic acids".

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Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

There was a recent study that claimed that the appearance of lighter skin of Europeans might have been related to the domestication of cattle. I was misleading, I didn't mean that lactose tolerance was necessarily related in any way. It was just another example of an adaptive process.

Right, dietary products don't themselves include much vitamin D but they do have the chemical compound necessary for skin to produce it.

__________________
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

All of your genes come only from your mother or your father. I suspect what you meant was whether there are some genes that all humans get from their fathers or that all humans get from their mothers, so they're only passed down through the generations along the male "line" or the female "line".

Genes on the Y chromosome are only inherited from the father. Genes on a boy's X chromosome are inherited only from his mother. Genes on the X chromosomes in a girl work like the other 22 chromosome pairs: one chromosome from each parent... with the twist that unlike the other 22 chromosome pairs, her father's X chromosome certainly came from his mother, not from his father or a recombined mix, so the girl essentially gets one of those from her mother and one from her father's mother.

In animals that use a system like ours to determine sex, with one type of chromosome only present in one sex (like the Y in male mammals and the W in female birds) and the other type present in both sexes (like the X in mammals and the Z in birds), the one that's only present in one sex (Y/W) tends to evolutionarily start shrinking soon after first acquiring its sex-determining gene(s), by losing genes that aren't related to the jobs of sex determination and sexual function. All that's left on the human Y is the small number of genes that make the body develop as male instead of as female and control the production of sperm cells. Meanwhile, the other sex chromosome, the one that's present in all members of the species (X/Z), retains the genes it had back when the sex chromosomes were a "normal" chromosome pair, before they began getting used for sex determination. This can include genes for any traits, no matter how seemingly unrelated to sex or to each other.

My question was more around question 4 in the OP rather than question 1. Is it true that human DNA can only encode "a few billion" bits, and is that enough to build a human, or are there information-creating processes needed to finish the "programming"? Our brains are trained by experience to build certain connections, so is the information to build the connections all that counts, or is the information in the connections themselves also important? I heard that as what you were saying, but I wanted to clarify the importance of that.

The genetic code is a program. But instead of binary and bytes it uses a base four system of four nucliotides divided into tri-nucliotide codons of giving a total of 64 different codons. This program can't produce anything unless it is placed in an automated factory called a cell. One is useless without the other. Genes switch on and off and give instructions according to the chemical environment they are in, that is, the chemical environment inside the cell. At one point you were a single cell in a chemical solution that triggered the divide rapidly part of your program and you became a blastolyst and eventually an embryo. If a cell can be tricked into thinking it is in that environment again it can be used to make a clone under the right circumstances, but we currently can't do this sort of cloning with mammals but we can transfer DNA from a body cell into an egg cell and produce a clone that way.

NOTE: I refer to a cell as an automated factory as an anology. To believe that a cell really is an automated factory made by someone is as silly as an adult believing that Santa Claus is the one who puts the presents under the tree. Also, DNA is not a blueprint, it is more of a recipe. For example your DNA doesn't contain a map of your fingerprints any more than a blueberry muffin recipe contains a map of where to place the blueberries. Their location is the result of chance.

That's quite interesting. It suggests that there are really three determiners of our attributes: nature, nurture, and... chance! Chance plays a role in nurture (which chromsomes you get, mutations and errors, etc.) and in nature (disease, injury, etc.), but it seems like embedding it in those other two does not do it justice-- when there is no identifiable factors in either nature or nurture that control your fingerprints, chance needs a designation of its own as well. One wonders-- what other attributes are like fingerprints? Aspects of intelligence, for example?

Santa does put the presents under the tree! Don't tell me skeptics have to be Santa unbelivers as well as atheists (Which I'm not.)!

__________________
I want to go back to the moon.
I don't care which rocket you use, whichever one you pick, I'll like it, I swear.
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek

Have you got a link?

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"A witty saying proves nothing" Voltaire.
"All your bias are belong to us" Ara Pacis.

It's only silly to believe in Santa Claus if you're an adult. Personally I hope to never be one of them. I plan to remain five years old and be perpetually asking, "Why?" for eternity.

Perhaps I should explain further why I think it is silly to believe that cells were designed. It is because they show clear evidence of being hobbled together and make use of whatever works rather than what would be a logical and intelligent design. When you consider things on a larger scale and look at the human body it is obvious that it was not logically designed or if it was designed it was by something with a weird sense of humour. The lack of intelligent design in the human body is especially apparent to males who have to walk around with their reproductive organs on the outside of their body.

It depends on what you mean by 'describable.' If you are asking, 'can I specify a particular sequence of DNA uniquely using only a sequence of four base pairs?" then the answer is 'yes.' However, based on your second question, I am guessing that's not what you meant.

Given that a cat has been cloned and the clone looks little like its clone (except insofar that both look like cats) I'd say that the determination of how genes operate is still very much a black box. Oh sure, we know about alternative splicing, siRNA, microRNAs, transcription factors, chromatid organization, recombination, etc., but getting from sequence to function is not [yet] fully characterized.

We already knew from identical twin kittens that fur colour patches are largely randomly determined and cat breeders had also worked out that in some cases fur colour is also affected by the temperature the kitten is exposed to while young. So someone knowlegable about cat genetics wouldn't expect cloned cats to look the same.

Nope, couldn't find it.

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Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

I asked because my recollection was a little different. I thought what they had discovered was a mutation associated with the light skin of northern Europeans, which might be associated with a diet based on agriculture. But I thought you could be talking about some other discovery...

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"A witty saying proves nothing" Voltaire.
"All your bias are belong to us" Ara Pacis.

Again the role of chance seems fundamental, even beyond its role in establishing the DNA code during reproduction, for some things we don't care that much about. What about for the ones we do-- like personality and intelligence? Is it possible, for example, for a dominant gene to not be expressed due to some chance process?

I think your intuition is correct. I remember reading, or hearing (can't recall where) that at the start of the 20th century biologists expected genetic material to be considerably more complex than it turned out to me. They were a bit surprised with what they found since the sixties.
The unexpected simplicity and sparseness of our DNA is evidence in favour of evolution / against ID, by the way. Clearly, fairly simple building blocks can lead to stunning phenotypical variety.

__________________
"A witty saying proves nothing" Voltaire.
"All your bias are belong to us" Ara Pacis.

Very little, if any. The number of choromosome pairs varies greatly between species. Fruit flies have just four pairs, while some species of fern have over 600. Chimpanzees and gorillas have 24 and humans have 23 -- it seems that two chromosomes fused when our species was formed.

We can't clone humans today.
Hypothetically, we may be able to do so in the future, but cloning Newton's genome is not the same as making an exact replica of Isaac Newton. He did not equal his genome. What made Newton into a genius -- his genes, his childhood, his society and times, all of the above? And be careful what you wish for; he was also a bit of a *******.

__________________
"A witty saying proves nothing" Voltaire.
"All your bias are belong to us" Ara Pacis.

I guess you're right... my recollection is only vague.

__________________
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

It was probably this press release you were thinking of.

Better summary here.

Oops, it seems the connection to agriculture was just my memory filling in too many gaps...

__________________
"A witty saying proves nothing" Voltaire.
"All your bias are belong to us" Ara Pacis.

No, it was much more recent, from this fall.

__________________
Science is a way of trying not to fool yourself. The first principle is that you must not fool yourself, and you are the easiest person to fool.
-- Richard Feynman

I'm eight forever. As Goud said "Science and belief need not be enemies."

__________________
I want to go back to the moon.
I don't care which rocket you use, whichever one you pick, I'll like it, I swear.
"If you think the LHC will create black holes, you might as well believe Hobbits are at the bottom of your garden."- Dr. Mike Inglis
Rovers forever! - ToSeek

I'm not sure I believe the table in front of me exists. For the sake of convenience I assume it does as it hurts if I try to walk through it.