DNA, Blueprints and laymen

[salm]

Hi,
Being a complete layman on this subject i allways thought that the blueprints for every form of life is in its DNA. Now somebody told me that, that´s what everybody thinks but in reality it´s not like that. He didn´t give that many reasons for his claim but it got me interested anyways.

Many online sources i´ve checked say that DNA can be referred to as an organisms blueprint or cookbook. Unfortunately non of these sources tell me why or how we know that the DNA is a blueprint.

However i found out that Proteins are the base of cels. Proteins tell the cells what kind of structure and function cells are supposed to have.
These proteins are formed from DNA and ribosomes with the help of RNA.
RNA transprots information from the DNA to the ribosomes, so the ribosomes "know" what kind of protein they´re supposed to form.


Questions:

- During Transcription, how does the mRNA know which part of DNA it needs to copy?

- How do we know that DNA is the blueprint; what kind of experiments can be done to find this out?

-If proteins make cels and RNA makes Proteins and DNA makes RNA where does the information when to make what and esspecially where to make what come from?
For example how does the organism know what part of DNA to copy in order to form a cell which is necessary to be part of the liver?


Help educate me.

[Base Delta Zero]

- During Transcription, how does the mRNA know which part of DNA it needs to copy?

There are 'begin' and 'end' tags that delinate specific genes for the production of the proper proteins, but other than that, no one really seems to know.

- How do we know that DNA is the blueprint; what kind of experiments can be done to find this out?

Well, by changing the DNA, you change the creature, which pretty much suggests that...

-If proteins make cels and RNA makes Proteins and DNA makes RNA where does the information when to make what and esspecially where to make what come from?
For example how does the organism know what part of DNA to copy in order to form a cell which is necessary to be part of the liver?

We're still working on figuring this one out...

[Vendetta]

Hi,
Being a complete layman on this subject i allways thought that the blueprints for every form of life is in its DNA. Now somebody told me that, that´s what everybody thinks but in reality it´s not like that. He didn´t give that many reasons for his claim but it got me interested anyways.

The reason that DNA is not a blueprint is because transcription is one way.

An architect can look at a building and reproduce it's blueprint simply from precise inspection. A geneticist cannot reproduce an organism's DNA in the same way.

DNA is a recipe. It describes the ingredients and what to do with them, but once you've followed the instructions you cannot show the result to someone and have them precisely reproduce the instructions (though they may be able to narrow some parts down, depending on their experience.)

This is explored further in, I think, River out of Eden. I seem to recall reading it there. (River is more aimed at the layman than The Selfish Gene, though the latter is quite readable)

[Ariphaos]

The reason that DNA is not a blueprint is because transcription is one way.

An architect can look at a building and reproduce it's blueprint simply from precise inspection. A geneticist cannot reproduce an organism's DNA in the same way.

This analogy doesn't hold, a more appropriate comparison would be for someone mildly familiar with the concept of a transistor and the ability to construct basic gates to re-build the blueprint of a 6th-generation processor based solely on information gained via input and output.

Just because it's too complex to currently understand does not mean it is not a very similar concept.

[dworkin]

Hi,
Being a complete layman on this subject i allways thought that the blueprints for every form of life is in its DNA. Now somebody told me that, that´s what everybody thinks but in reality it´s not like that. He didn´t give that many reasons for his claim but it got me interested anyways.

An organisms growth and development is mediated by more than it's genes although when you look closer you often find genes further down the causal paths.

For example, your development as a fetus was mediated largely by conditions in your mum's womb. So, in a sense the genes in your cells were not wholly responsable for your development. However copies of half those genes were in your mum's cells which were responsable for the placenta's conditions at which point I'll return to Go and collect $200.

Your genes, especially the maternal compliment were responsable for your embryological development. They just wer'nt in any cells that were specifically you. They were in your mum.

Many online sources i´ve checked say that DNA can be referred to as an organisms blueprint or cookbook. Unfortunately non of these sources tell me why or how we know that the DNA is a blueprint.

It's a nice quote. It helps people understand what the genome does. It's just not the entire story. Plenty of experiments have verified that infomation is contained in the nuclear material and were performed before the structure of DNA was known.

Try "mouse, virus, DNA" as search terms.

However i found out that Proteins are the base of cels. Proteins tell the cells what kind of structure and function cells are supposed to have.
These proteins are formed from DNA and ribosomes with the help of RNA.
RNA transprots information from the DNA to the ribosomes, so the ribosomes "know" what kind of protein they´re supposed to form

And lipids and sugars. But they're assembled by enzyme actions which are modified peptides produced by RNA synthesis so again I can return to Go...

- During Transcription, how does the mRNA know which part of DNA it needs to copy?

There is no 'know'. Most DNA in any cell is tightly 'wound up' on the chromosome and unreadable. However DNA can be 'unwound' through the action of promotors and inhibitors due to changing chemical conditions based on the current demands of a cell. When DNA is unwound it is readily transcribed, initiating synthesis of a peptide chain and ultimatly production of a protein or enzyme.

It's all chemistry. And the above is still a 'simple model' only. Gene regulation a is very complex thing.

- How do we know that DNA is the blueprint; what kind of experiments can be done to find this out?

An experiment done in the 30's IIRC tested wether the nuclear component of a virus or the protein component contained the information needed to make new virii.

It's also repeated every time someone inserts or modifies a gene in an organism.

-If proteins make cels and RNA makes Proteins and DNA makes RNA where does the information when to make what and esspecially where to make what come from?

Proteins are formed from amino acid chains which use mRNA as a production template and mRNa is formed using DNA in much the same manner. All this formation is based on the chemistry of a living cell.

Nucleic acid chains are excellent replicators, under good conditions and with a plentiful supply of raw material they'll form copies. It's all based on some elegant organic chemistry and hydrogen bond formation.

You can cause DNA to replicate in a test tube filled with an aqeuos solution of nucleic acids and some DNA transcriptase. It pays to have a beaker of water and hot plate too. It's a chemical reaction.

For example how does the organism know what part of DNA to copy in order to form a cell which is necessary to be part of the liver?

Large bits of your genome produce regulator, inhibitor, mediator and promotor molecules. All these interact with a cell and it's environment to activate only certain gene combinations for certain cells.
During development a series of fairly ubiquitous genes labled Hox genes are thought to be responsable for early development and differentiation of cell types.

I recomenrd the 500 sectio of your local library for further reading.