It's a 3 billions years long answer that you are asking, so it's just not the right place to discuss. For example there is no "chromosomes in DNA." the chromosomes are mostly DNA double helices (to make the things overly simple).

Hi Robert,

I was of the understanding that chromosomes are found in the strands of the double DNA helices and unzip to form the 22 pairs of chromosomes involved in the cellular process to form the proteins.

Maybe my question is better suited to the philosophy forum?

Chromosome has a Greek root, meaning something like "colored body" because some scientists long time ago, while using some dyes to stain cells, found a "colored body" inside these cells. Later it was revealed that this colored body was made of DNA. then rather than a single body people found that they could differentiate several individual elements, the chromosomes. there are 23 pairs in normal human cells, but the number varies with the species considered.

So in a nutshell:

Chromosomes are the "storage format" for DNA. Every cell in any organism has, as a general rule, the entire full complement (genome) of DNA required to encode that entire organism, and that genome is broken into pieces (the chromosomes). Humans are diploid, meaning that there are actually TWO copies of each chromosome (one from the father, one from the mother). Naturally these chromosomes will be slightly different from each other - and in fact different from those found in the parents, since the process of meiosis, which generate the sperm/egg (gametes, or germ cells) that formed the individual, naturally introduces mutation - the process of chromosome replication is flawed and not perfect.

Okay, so Chromosomes are made of DNA, which is the storage format for the human genome, which is the blueprint for the organism, and each cell has a copy (or technically two). Now: the chromosomes will make transcripts of the genes (think of making a copy of just part of that blueprint) and send those to Ribosomes, where the transcripts are expressed - read to make the actual protein corresponding to that gene.

Gene expression is huge. I'm not going to explain a lot of it, but suffice it to say that each cell type (e.g. liver, or heart, or skin) only expresses the genes that are required to be that kind of cell - even though the cell contains the full blueprint. Yes, it's fiddly to control and complex.

More complexity - remember that there are maternal and paternal copies of the genome in each cell? Now that comes into play in expression, as both the maternal and paternal copies of genes get expressed (again, over simplified and not 100% accurate, but a sufficient explanation). If those copies of genes are the same, no worries - if they are different, now you have a "blending" effect, as slightly different proteins are made for the same purpose.

And it's even more fiddly - because proteins can also interact with other proteins, and they can be modified (post translational modification).

But to get back to your question - proteins are just molecules, they have functions, and those functions differ and vary. No proteins emit electrical impulses, but they may contribute to structures (e.g. neural cells) which as a system do have larger functions.

I would recommend that you pick up a copy of James D. Watson's "Molecular Biology of the Gene" and read it through. It gives you a solid background in both genetics and molecular biology, but in a digestible way - and in a way that replicates the historical discovery processes in the fields, so it really does build up to a logical story.

LOL, John. Yes. We're always encouraged *not* to use Wikipedia as a "primary reference" in our teaching, but - Yes. Sufficient unto the day.

Honestly, Mr Inberg, you'll have some serious readings in science to appreciate the whole concept (and I mean no offense here). This is a complex question and your introduction also shows that some physics might show its use.

In a proper order:

1. Mr Rumpf and Wiendenhoeft suggested good starts (and provided good explanations).

2. Just to mention it, no protein whatsoever is produced with a color- never. Color begins to exist in the eye of the observer: light hits an object (or molecule!) and due to the spectrum of light absorbed, another spectrum is reflected and therefore the eye and observe the reflected light and consider this spectrum as a color. Therefore, color is not emitted, just a reflection of light (black= full absorbance -in the human-visible spectrum- and white= full reflection).

3. I also made point 2 as an introduction for another thing: the genes don't necessarily produce their products for what we see of it. The melanin pigment of the skin is produced (evolutionarily-understanding) to protect genomic DNA (genes) from the effects of sun, that could damage our genome: it is absorbing visible light, therefore this light does not go any farther. It absorbs significantly, so guess which color we see melanin? Brown-black. But making color is not its purpose.

4. Now to be more helpful, I'll compare gene expression to a society. All genes have one function (at least) encoded in their sequence, a function that can often be predicted by their sequence: enzyme, structural... But it really is their regulation and interaction that decides of what they'll do! Jus like humans have jobs and it is the interactions of humans that decide of the look of a city (also civil engineers, but it's part of the game!). Road workers make road and would not stop, it is their task. But their supervisor, what he does is to make them stop when they reached 1 km (or the union, depending on your view on the topic- joke apart!). And the civil engineer that wants a certain road, say of 5 km will put a supervisor (express a gene) only after 4 km! It is all a matter of regulation like that.

5. We have 30000 encoded genes in the human genome (grossly, it is not precise and they don't all work, just for the need of the discussion). All of them have at least one function. So 30 000 type of jobs in the body. Most of them can interact with each other to multiply the possibilities... So it is about endless. This is why humans and mice have 98% homology (our genome is 98% similar) but don't look alike (well sometime some people are rats, but it's different...).

So these 30 000 workers (genes) are in the cells. But they are not needed all the time! So you ask to work a certain set in one cell at a time (consider the cell as a city): if you don't live at the coast, no need to ask fishers to come to work! So certain genes are not called to action in a cell. The ones that you plan to need, you "express" them: you start producing their messenger RNA (mRNA). This puts them into a form ready to serve, like calling a worker in the morning and telling him to stay on call. This forms your mRNA pool, or worker force. When you actually need the work of one of them, you call him to work: you translate its mRNA to protein. From now on, the road worker is making a road. Many roads to do? call many replicates of the worker! The road has to be 5 km, so after 3,5 km, the civil engineer (a gene itself) calls the supervisor and asks him to come to work. He arrives by 4km. When it is 5, he stops the workers and tell them to go home!

From that simple example, you can see how you can create all muscles, that are made of the same material (depending on their type, leave that apart): some are long some short: they have to go from one attachment point to another, so these are the signals (attachment) that signal start and stop of the growing os the muscle (in lay terms, in fact it is more complicated, but hey, life can deal with that: 30 000 genes!). And in living organisms everything is broken into simpler tasks until one simple gene can effect one action. And it is their INTERACTION that decides of the final result. Melanin is expressed by all human beings. The color of your skin is dependent on how much your body calls this worker into action or not (Knowing that, please, pretty please stop talking of human races based on skin color, just one race). Hair is different color? True, and this is dependent on the protein that we put in the hair: their proportion and yes, their color. The differences in the genes sequence can change their light absorbance capacity, but maintain their structural function (like for hair: keeping you warm).

So take-home message: yes some characteristics depend on only 1 gene and the difference might be visible, like eye colors, but the interactions decide of most, like ultimately the shape of a body.

I hope this gives you the state of mind to have when considering biology! Cheers.

Hi Phillipe, is mRNA a single strand chromosome or a double helix chromosome pair like DNA chromosomes; and is there a mRNAstrand (or pair of strands) for each DNA chromosome pair in the cell nucleus?

Thanks

Marc, you're still confusing the structural elements. DNA is double-helical and gets packed into chromosomes. It's the blueprint with all the instructions for making proteins. The DNA in chromosomes gets "read/transcribed", creating an mRNA (single strand) copy. This goes to ribosomes and is read to make a protein. There's no conversion, each molecule is read by enzymes which then construct the next form. mRNA is transitional, it is used to transfer the data, and then gets degraded. Since you are at the University of Western Sydney, it seems likely that you could audit a few undergraduate courses in molecular biology to get the background you need....

thanks Robert for the suggestion but I am probably going to get better answers from RG; plus it is more convenient for me due to my commitments and semester is finishing up at UWS with undergrads going on summer break. I wasn't actually suggesting that there was a conversion taking place even though it may have come across that way in my question. I just wanted to find out if anyone knew of the the more rigorous detail involved in genes unzipping from a chromosome pair and binding to mRNA in the cell nucleus before the process of protein construction in the cell body. The laymen literature just seems to explain it just like that with no further detail such as if the four different types of blood cells are formed by four different sets of genes unzipping from the chromosomes and binding in a different sequence to the mRNA nucletoide bases.

Also, do cross-linked pairs of genes actually unzip from the chromosome pair and then bind in a single strand to the mRNA strand?

I guess the problem I have is the lack of visual illustration in the literature of the more rigorous detail involved in gene expression.

Try this video - it shows how the Chromosomal DNA is read to produce mRNA....

http://www.youtube.com/watch?v=JOBwqwxgJqc&feature=related