contrarian
Registered Senior Member
Seems like you're making my point here: If there are no genes that create specific organs then how are they created?
Evolution vs Creation
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Seems like you're making my point here: If there are no genes that create specific organs then how are they created?
Originally posted by contrarian
Seems like you're making my point here: If there are no genes that create specific organs then how are they created?
by creating positional information
contrarian
Registered Senior Member
Spurious
It seems to me you're being excessively vague. I've read some of these books, but they end up talking in circles too.
Ok, so genes don't build organs, positional information does - but how does that work - how are the messages transmitted cell to cell so they form the correct shape. Unless you can describe it or define it - it ends up being meaningless.
in what medium is positional information transmitted? - where does it come from- what molecule stores it. How does it move through the organism's life cycle. DNA does not change
My basic premise is that (a) genes are not the complete answer to morphology and
(b) we can't explain what else is involved
Thus, we really don't understand morphology
Cheers,
It seems to me you're being excessively vague. I've read some of these books, but they end up talking in circles too.
Ok, so genes don't build organs, positional information does - but how does that work - how are the messages transmitted cell to cell so they form the correct shape. Unless you can describe it or define it - it ends up being meaningless.
in what medium is positional information transmitted? - where does it come from- what molecule stores it. How does it move through the organism's life cycle. DNA does not change
My basic premise is that (a) genes are not the complete answer to morphology and
(b) we can't explain what else is involved
Thus, we really don't understand morphology
Cheers,
contrarian,
the problem here is that your don't know nothing, sorry to say it but you can not argue for or against a side if you have little knowledge of the subject.
Cell communicate is chemically. Hormones, lingants, ect in the environment cell activate specific genes and curb production of specific proteins: thus do as it should and become say a liver cell. We know this is true of many morphological traits, true we don’t know everything, but the present theory of morphologic match well with the evidence.
the problem here is that your don't know nothing, sorry to say it but you can not argue for or against a side if you have little knowledge of the subject.
Cell communicate is chemically. Hormones, lingants, ect in the environment cell activate specific genes and curb production of specific proteins: thus do as it should and become say a liver cell. We know this is true of many morphological traits, true we don’t know everything, but the present theory of morphologic match well with the evidence.
I'm so pro-evolution. Just the finesse of it is mindboggling, Though understandable ofcourse.
But get this: EVOLUTION, has been speeding itself up.
It brought forth humankind, to help it excellared itself.
And due to the advent of bio-engineering we and it can fully explore all it's potentials. At speedreduction from 10.000 years to around 5 to 10 years.
No thats progress
But get this: EVOLUTION, has been speeding itself up.
It brought forth humankind, to help it excellared itself.
And due to the advent of bio-engineering we and it can fully explore all it's potentials. At speedreduction from 10.000 years to around 5 to 10 years.
No thats progress
Originally posted by contrarian
Spurious
It seems to me you're being excessively vague. I've read some of these books, but they end up talking in circles too.
I’m not vague, I am just using the terminology that goes with the field. If I say positional information and if you have read ‘these’ books, then you would know enough. Therefore I am not convinced you read any.
once again…you seem to be on such a basic level of knowledge that I couldn’t explain this in one post. Cells communicate with each other all the time. An oocyte already starts with positional information, because an oocyte is never homogenous (for most species). Interactions between a few groups of signaling molecule families fine-tune and add this original positional information. See the references below for more information.
Originally posted by contrarian
My basic premise is that (a) genes are not the complete answer to morphology and
(b) we can't explain what else is involved
Thus, we really don't understand morphology
Cheers,
people have been studying the ‘development of morphology’ for a long time. The postulation of the theory of evolution acted actually as a cathalyzer in this field. I could now mention the most obvious exmaples, but will point out a less known fact. This is for instance the reason marine biology stations began to appear round and after 1870. They thought that the answers to evolutionary problems could be found in the seas and oceans, and one of the most important disciplines was the study of the origin of morphology, developmental biology. It has been a tremendously active field, and I really find it weird that you supposedly read books about it, but do not seem to know any of the basics. Forgive me for being skeptical, but that is how is feels to me.
But here; I did your homework for you, developmental biology is also online. Here I typed in positional information in the search engine:
http://www.ncbi.nlm.nih.gov:80/entr...ch&term=positional+information+AND+dbio[book]
original link to developmental biology
http://www.ncbi.nlm.nih.gov:80/books/bv.fcgi?call=bv.View..ShowTOC&rid=dbio.TOC&depth=2
pubmed bookshelf
http://www.ncbi.nlm.nih.gov:80/entrez/query.fcgi?db=Books
Last edited:
Originally posted by contrarian
Seems like you're making my point here: If there are no genes that create specific organs then how are they created?
contrarian
Registered Senior Member
Thanks for the input guys
Maybe I'm just dense but I still can't get this straight:
What is positional information, physically?
Is it a gene or sequence of genes or something else?
Maybe I'm just dense but I still can't get this straight:
What is positional information, physically?
Is it a gene or sequence of genes or something else?
Position information is the interaction of chemical messenger with the analog computing center of cells (aka, genes, operon, protein curbing, introns, ect) it is a complecated system of input/output feed back loops and so forth.
Postional information:
well...it is not easy to give a simple explanation of course. But an embryo starts of as a fertilized egg. This egg is not an empty piece of paper which needs to be coloured in. It already has information in it. Proteins and such are not distributed evenly in the egg and fertilization itself supplies new information in some cases.
The oocyte contains very raw information. For instance, the anterior-posterior (from front to back)axis is already defined, albeit roughly by a certain distribution of molecules. The exact details are all dependend on the species. This rough postional information is then fine-tuned. This is usually done by so-called signaling molecules.
These are proteins that are excreted from one cell and can bind to an receptor on another cell. Once bound to the receptor it can activate for instance the expression of a specific gene in that cell, or it can maintain expression of another gene already expressed, or shut expression down.
One classical way to specify more positional information is through a morphogenetic gradient. A signaling molecule is released by cells in a certain region and the molecules can travel through the tissue and activate receptors a long distance away from the source. Moreover, the distribution of this signal will resemble a gradient. The signal is strongest near the source, and weaker away from the source.
This can also be used to specify even further positional information. Certain genes only turn on at specific concentrations. Along the gradient different gene expression can then be induced in different regions. And this specification of more complex information is all based on a single group of cells expression a morphogen.
One can complicate matters even further, by setting up a system with 2 morphogradients. For instance in case of our basic anterior-posterior system we could have one source at one end of the egg and another at the opposite end. The interaction of 2 gradients allows for even further complexity and generation of more information.
Where do the organs know where to go? An embryo has more than one axis. Besides the anteriorposterior axis there is for instance the dorsal-ventral axis. The place where 2 of these axes intersect can basically define the postion of an organ (in some cases). Rough postional information made along two different axes are then combined into qualitative new information.
etc etc...
we are only scratching the surface here.
well...it is not easy to give a simple explanation of course. But an embryo starts of as a fertilized egg. This egg is not an empty piece of paper which needs to be coloured in. It already has information in it. Proteins and such are not distributed evenly in the egg and fertilization itself supplies new information in some cases.
The oocyte contains very raw information. For instance, the anterior-posterior (from front to back)axis is already defined, albeit roughly by a certain distribution of molecules. The exact details are all dependend on the species. This rough postional information is then fine-tuned. This is usually done by so-called signaling molecules.
These are proteins that are excreted from one cell and can bind to an receptor on another cell. Once bound to the receptor it can activate for instance the expression of a specific gene in that cell, or it can maintain expression of another gene already expressed, or shut expression down.
One classical way to specify more positional information is through a morphogenetic gradient. A signaling molecule is released by cells in a certain region and the molecules can travel through the tissue and activate receptors a long distance away from the source. Moreover, the distribution of this signal will resemble a gradient. The signal is strongest near the source, and weaker away from the source.
This can also be used to specify even further positional information. Certain genes only turn on at specific concentrations. Along the gradient different gene expression can then be induced in different regions. And this specification of more complex information is all based on a single group of cells expression a morphogen.
One can complicate matters even further, by setting up a system with 2 morphogradients. For instance in case of our basic anterior-posterior system we could have one source at one end of the egg and another at the opposite end. The interaction of 2 gradients allows for even further complexity and generation of more information.
Where do the organs know where to go? An embryo has more than one axis. Besides the anteriorposterior axis there is for instance the dorsal-ventral axis. The place where 2 of these axes intersect can basically define the postion of an organ (in some cases). Rough postional information made along two different axes are then combined into qualitative new information.
etc etc...
we are only scratching the surface here.
contrarian
Registered Senior Member
Hi Spurious
Hope you're enjoying this as much as I am.
Couple of things
I just like to be precise: In the egg - are you talking about positional information being some kind of pattern in the cytoplasm or are you talking about some kind of 'pre' positioned enzymes and other proteins in distinct places?
Morphogens are proteins, I assume. Is there more than one kind?
How does the positional info get into the egg to begin with?
Has anyone ever tried sucking out a chunk of a fertilised egg's cytoplasm to see if you can cause an organism to be born without a particular organ?
What happens when you implant the genetic material from one species into an egg from another species that has its genetic material combined?
Peace
:m:
Hope you're enjoying this as much as I am.
Couple of things
I just like to be precise: In the egg - are you talking about positional information being some kind of pattern in the cytoplasm or are you talking about some kind of 'pre' positioned enzymes and other proteins in distinct places?
Morphogens are proteins, I assume. Is there more than one kind?
How does the positional info get into the egg to begin with?
Has anyone ever tried sucking out a chunk of a fertilised egg's cytoplasm to see if you can cause an organism to be born without a particular organ?
What happens when you implant the genetic material from one species into an egg from another species that has its genetic material combined?
Peace
:m:
My anolgy was not ment to ne accurate it was ment to point out a
Yes, more then we have counted, also many are not proteins but are purely chemical such as steroils.
Genetically, initial genes turn on and the process is feed back looping.
Yes they have, I'm sure spuriousmonkey can give you very specific examples, I can only remember the rouhg details of a couple.
It depends on how you implant it and how what his genetic material is and does. Usually if you inject a gamete of one species (or even the same species) into a already fertilized ego of another, the result so total cell death from incompatible genetic instructions and production over load. Inserting a gene or two with the use of a virus or plasmid victor is much more successful, the product has the new transgenic gene inserted (randomly somewhere) in its genome and will (hopefully) activate it. For example: the goats with spider silk protein gene inserted so that they produce viable spider silk protein in their milk that can be used to make super strong and cheap polymers.
Yes, more then we have counted, also many are not proteins but are purely chemical such as steroils.
Genetically, initial genes turn on and the process is feed back looping.
Yes they have, I'm sure spuriousmonkey can give you very specific examples, I can only remember the rouhg details of a couple.
It depends on how you implant it and how what his genetic material is and does. Usually if you inject a gamete of one species (or even the same species) into a already fertilized ego of another, the result so total cell death from incompatible genetic instructions and production over load. Inserting a gene or two with the use of a virus or plasmid victor is much more successful, the product has the new transgenic gene inserted (randomly somewhere) in its genome and will (hopefully) activate it. For example: the goats with spider silk protein gene inserted so that they produce viable spider silk protein in their milk that can be used to make super strong and cheap polymers.
feels more like homework to me…Originally posted by contrarian
Hi Spurious
Hope you're enjoying this as much as I am.
yes proteins (transcriptionfactors, signaling molecules, enzymes etc) are not usually randomly distributed in an egg. It depends on the organism in question how this distribution occurs. In developmental biology the question what was first, the chicken or the egg, is a real conundrum, since you would need the mother to make sure that the determinants are properly distributed in the egg. Aand you need an egg to make a chicken.
…also in some cases during fertilization the point of entry of the sperm causes the ooplasm (the cytoplasm of the oocyte) to rotate, or orientate in a certain manner.
correct, with the remark that not very many true morphogens are known actually. There are many signaling molecules that apparently act as morphogens, but they don’t do this exactly through a gradient. There are other ways to do this. Decapentaplegic would be a legitimate morphogen. Maybe it goes to far to discuss here what the essence is of a legitimate morphogen is. It goes quite deep.
Cells surrounding the egg deposit these determinants in a particular pattern. Depending on the organisms these cells have different names and function differently. Also as said before the sperm entry point can determine polarity. And also some eggs are very yolky, which also acts as polarizer, since yolk doesn’t mix very well with normal cells.
Yes…standard old classical stuff for instance in the fruitfly research. For instance maternal (deposited by the mother) ‘Bicoid’ RNA is present only in the anterior (front) part of the oocyte. If you mutate the gene (make it inactive) or extract the cytoplasm here, the head and thorax are deleted. They are replaced by an inverted telson (the most posterior/back structure normally). The front is therefore turned into a back. You could inject wildtype anterior/frontal cytoplasm into this region to resque the bicoid mutant for instance. They will be normal now.
You could inject a mouse gene into a fruitfly mutant to resque it. Not in the case of bicoid, because the vertebrate homologue of bicoid is too different. But it works for other genes.
contrarian
Registered Senior Member
Thanks for your assistance, Spurious
I'll have to metabolize what you told me for a while.
I always find it fun to take an unusual stance and see how far I can go with it.
You've been a really good sport in this regard.
Just a couple parting shots.
I presume this system of positional information continues all down the line? ie: when a cell differentiates to a dermal skin cell and an epidermal skin cell it uses pre positioned proteins in the precursor cells?
How exactly does a cell determine if morphogen levels are too high/low? This seems to involve an IF...Then type of statement rather than simple activation of a gene.
Au revoir
I'll have to metabolize what you told me for a while.
I always find it fun to take an unusual stance and see how far I can go with it.
You've been a really good sport in this regard.
Just a couple parting shots.
I presume this system of positional information continues all down the line? ie: when a cell differentiates to a dermal skin cell and an epidermal skin cell it uses pre positioned proteins in the precursor cells?
How exactly does a cell determine if morphogen levels are too high/low? This seems to involve an IF...Then type of statement rather than simple activation of a gene.
Au revoir
probably not. We were discussing mainly the early events of generating information. For the epidermis there is clearly a strong interaction with the underlying mesenchyme. This is reciprocal of course and dynamic. At one point in time the mesenchyme could determine the epithelium and look a few hours later and the roles are reversed. It is impossible to be general in commenting about this.
This is mainly done on the promotor level. if there are more binding sites in the promotor than it would be easier to turn a gene on. There can also be a combined effect of positive and negative acting binding sites.
Also the history of the cell often plays an important role in determining whether to react or not.