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Offline neilep

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Does A Cell have the complete picture ?
« on: 08/08/2006 22:39:02 »
When DNA instructs cells to what to become , is the complete picture (the eventual final priduct)there within the instruction  ? and that  only the necessary portion of the instruction particular to that cell as to where it should be is given yes ?

I know I'm not explaining this very well...but somewhere....all the cells come together to make a thing yes ?..either a human, a cat a virus...even wifey ?

Somewhere the complete and final product must ne known else,  where would the cells know where to go to create such a thing ?

Is this making any sense ?...  How does a cell at the end of my finger know that it has to be at the end of my finger ? it must also know the entire final product too

Help !!

Men are the same as women, just inside out !


 

another_someone

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Re: Does A Cell have the complete picture ?
« Reply #1 on: 08/08/2006 23:19:12 »
While I would not suggest that I am qualified to give a definitive answer to this, this is not at all my understanding of the way things are.  There is no clear overall blueprint, but just a set of relationships.  Each cell knows what it is meant to do in its particular environment, but nowhere is there an overall picture.

Don't forget that evolution is a matter of trial and error, and not a matter of grand design so there is no need for any grand design to exist.  The DNA is simply a set of instructions that says 'if you are in this environment then do this' it is like a computer program.  It is easy enough for evolution to test changing one instruction at a time within the program, and testing if the result is superior (within the niche that the organism is living in) to the previous instruction, and it can do that without any overall system design.

Ofcourse, you might say that the entire program is a kind of system design in itself, but it is a design from the bottom up, rather than the top down.



George
 

Offline neilep

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Re: Does A Cell have the complete picture ?
« Reply #2 on: 08/08/2006 23:37:40 »
THANK YOU George.

Yes, I can very easily see how the trial and error phenomena dictates as to the 'local 'ity of where the cell should be.

Let me say that I do not believe in Intelligent Design.

Is it a fair comparison to use a computer program as an analogy ?....because that does have a ' bigger picture ' purpose and is most definitely constructed by a designer. Please correct my errors , I'm also not a software engineer !

I suppose evolution/nature here then is the grand designer but I still think that if a cell is told that if you are in the area then behave like this that what ever has instructed the cell to do that must then receive some instruction also.

The blueprint for the final product must exist somewhere.

I really appreciate your answer George. Thank you again.




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another_someone

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Re: Does A Cell have the complete picture ?
« Reply #3 on: 09/08/2006 00:30:16 »
quote:
Originally posted by neilep
Is it a fair comparison to use a computer program as an analogy ?....because that does have a ' bigger picture ' purpose and is most definitely constructed by a designer. Please correct my errors , I'm also not a software engineer !



Any analogy will have its limitations.  One uses an analogy to translate something one is not familiar with into a domain one is familiar with.  I am very familiar with computers, and so it is a useful analogy for me to make but it may not necessarily work as well for someone else.

A computer program does not really have a bigger picture, it is the end product of a design, but it is not the design document itself.

A computer program has a purpose because the people who designed it gave it a purpose, but of itself, it has no innate purpose, it is merely a thing.

A computer program is a set of instructions to a computer, and the instructions are themselves just raw materials, like a lump of steel it is only when they are fashioned into something, that they become the thing, and what they are depends on how they are fashioned, and the purpose they have depends upon what purpose was intended by the person that fashioned it, and if no purpose was intended, then they have no purpose.


quote:

I suppose evolution/nature here then is the grand designer but I still think that if a cell is told that if you are in the area then behave like this that what ever has instructed the cell to do that must then receive some instruction also.



Yes, it does receive some instruction, but most of those instructions are not global, but local.

Think of it like a collection of businesses each business trades only with its neighbour (or some other business partner) the entire business community functions as a whole, but no single person has a design for how the business community works, it just works by the way the little bits all relate to each other.

Each business has its own set of rules, its own instructions, as to how it relates to its business partners, but it does so without any central authority (ok, I suppose you can say that the legislature provides a set of overall instructions, but those instructions are still not a blueprint).



George
« Last Edit: 09/08/2006 00:33:11 by another_someone »
 

Offline Mjhavok

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Re: Does A Cell have the complete picture ?
« Reply #4 on: 09/08/2006 08:53:12 »
Saying DNA is a genetic blueprint then can be a little misleading. An architects blue print shows you the exact dimensions of the house and with computer graphics technology you can get a very good idea of what the house will look like. I don' think you could look at the DNA and tell what someone was going to look like to the same degree. The final blueprint for each person can't be anywhere because until that person has been born they aren't complete. They aren't even complete when they are born but u know what I mean hopefully. You continually develop depending on your environment and ur eating habits etc. Ok enough nonsense from me.

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Offline iko

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Re: Does A Cell have the complete picture ?
« Reply #5 on: 09/08/2006 13:24:55 »
I think that studying homozygous twins lives from the cradle to the end of life we get lots of data about gene & environment interactions: if a certain disease is due to an inherited genetic defect, the incidence in twins will be much higher than in the general population.  If the cause is mostly environmental, the incidence in twins will be similar to the control population.
By the way, the risk of leukaemia in identical twins is only a little bit higher than the rest of the poeple...so the mysterious unknown cause of human leukaemia is probably...(Exercise n1)

iko
 

another_someone

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Re: Does A Cell have the complete picture ?
« Reply #6 on: 09/08/2006 14:48:59 »
quote:
Originally posted by iko
By the way, the risk of leukaemia in identical twins is only a little bit higher than the rest of the poeple...so the mysterious unknown cause of human leukaemia is probably...(Exercise n1)



I am not at all sure there is a single cause of leukaemia why should there be only one cause?

I think it is fairly certain that some leukaemias are caused by viral infections.

http://journal.paho.org/index.php?a_ID=273
quote:

It has been 25 years since the discovery of the first human retrovirus, human T-cell leukemia virus type 1 (HTLV-1) (1). Soon after HTLV-1 was discovered, a second human retrovirus, HTLV-2, was described (2). In 2005, two new human retroviruses, HTLV-3 and HTLV-4, were reported in central Africa (3, 4). HTLV-1 was the first retrovirus linked to human disease (5). It has been convincingly associated with adult T-cell leukemia/lymphoma (ATL), HTLV-1-associated myelopathy/tropical spastic paraparesis (HAM/TSP), uveitis, and infective dermatitis (6-9).
The viruses, especially HTLV-1, have a worldwide distribution (10). Although the exact number of individuals who are seropositive for HTLV-1 or HTLV-2 is not known, it is estimated that about 15 to 20 millions persons (mostly HTLV-1-seropositive) live with these infections worldwide (10). The areas of the world with the highest prevalence rates for HTLV-1 include southwestern Japan, several countries in sub-Saharan Africa, Central America, and localized areas of Iran and of Melanesia. Higher prevalence rates are also found in several countries in the Caribbean, and somewhat lower seroprevalence rates are found in several nations in South America (10). Known modes of HTLV-1 transmission include mother to child, predominantly through breast-feeding; sexual intercourse; and parenteral transmission by transfusion of infected cellular blood products or sharing of needles and syringes.
In the Caribbean, Jamaica and Trinidad and Tobago have relatively high (up to 6%) HTLV-1 or HTLV-1/2 seroprevalence rates in the general population or in specific groups of individuals such as pregnant women and prospective blood donors (11, 12). Although no studies with representative samples of the general population have been conducted so far in South America, lower seroprevalence rates are found in several countries, including Brazil and Colombia (10). Data from Argentina, Brazil, Colombia, and Peru are for the most part restricted to specific groups such as blood donors (up to 2% of seropositivity for HTLV-1/2), pregnant women, Amerindian tribes, and intravenous drug users. Several studies have reported that indicators of lower socioeconomic status, such as having fewer years of schooling, are associated with HTLV-1/2 infection in both endemic and nonendemic areas (13, 14). This suggests that social and environmental factors associated with poverty may influence HTLV transmission. Similarly, HTLV-1-endemic countries (except Japan) have low per capita incomes and fewer resources to deal with a higher burden of HTLV-1/2 infection and associated diseases. The impact of HTLV-1- associated diseases on individuals and their communities is often devastating. No preventive vaccine exists, and the prognosis for ATL and HAM/TSP is poor, in terms of both survival and quality of life (15). HAM/TSP is a longlasting, progressive disease, and the financial costs for the infected individuals, their families, and health systems are immense. Given these realities, public health interventions such as counseling and the education of high-risk individuals and populations are of great importance.
HTLV screening of donated blood has been routinely implemented in Brazil, Canada, the United States, and other countries in the Americas. Although no specific studies have evaluated this intervention, it has certainly diminished the occurrence of new infections among blood recipients. However, for many other countries in the Americas, this intervention is not systematic and/or permanent, or it is not done at all. The development of adequate, cost-effective strategies for HTLV screening of donated blood should be carefully considered in many countries in the Americas. Also, preventing mother-to-child transmission would probably have a substantial impact on the occurrence of HTLV-associated diseases. As is done for blood donations, prenatal screening for HTLV-1 should be implemented at least for countries, states, cities, or even smaller geographic units with high seroprevalence rates for HTLV-1/2. This should be done in combination with counseling of seropositive mothers regarding transmission through breast-feeding. Since HTLV can be transmitted through sexual contact, there should be an emphasis on condom use, avoiding multiple and unknown sexual partners, and not paying or receiving money for sex. Finally, utilizing counseling and education to encourage intravenous drug users to use harm reduction practices may be effective in preventing HTLV-1/2 infection in this population group.





George
 

Offline Carol-A

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Re: Does A Cell have the complete picture ?
« Reply #7 on: 09/08/2006 15:07:56 »
The environment of a cell will decide which genes are switched on or off. There has been a lot of work done on this, and it really is amazing! One are that is being ecplored is which genes are switched on and off to make teeth..... it would be useful to be able to regrow teeth. They now know which genes need to be switched on and off... even the difference between molars and canines. Some of this research came out of a study of certain cancers, where, for example, it has been observed in some ovarian teratomas (sp), teeth will actually grow. Anyway, although our DNA contains all the information, as it were, which bit is switched on where is largely due to position.
 

Offline iko

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Re: Does A Cell have the complete picture ?
« Reply #8 on: 09/08/2006 15:50:20 »

 
quote:
I am not at all sure there is a single cause of leukaemia why should there be only one cause?

I think it is fairly certain that some leukaemias are caused by viral infections.




Of course there is not a single cause for leukaemia, I meant that its origin is probably not genetically determined (apart from some toddlers in which some genetic damage has been demonstrated looking back at the DNA sampled at birth for screening tests).
In most mammals it is a viral and infectious disease. Feline leukaemia in cats is an easy model: cats get the FeLV bug, develop a flu-like disease and neutralizing antibody to get rid of it. In some animal no antibody comes out (defective immune reaction?), viruses persist for a certain time and damage cell precursors, then a leukaemia or lymphoma start.
In humans it doesn't seem so easy and crystal-clear.  Thanks to Bob Gallo HLTVI has been found in a small subgroup of human T-cell leukaemias in 1981...He was almost the last researcher who studied new human viruses in leukaemia and so spotted the AIDS retrovirus shortly after.
Epstein Barr Virus is perhaps involved in some leukaemia or lymphoma but the mechanisms are still unclear.
Mel Greeves's hypothesis (the last "hit" may be infectious)is neat:
A series of genetic mutations make a cell clone expand a bit too much, then a strong stimulation (overidden immune response to an infection by a common pathogen: strepto, mycoplasma, adenoviruses, toxoplasma,CMV, EBV, parovirusB19 etc.) leads to sustained growth of the expanded clone and starts bone marrow and organ invasion.
The environment(infection-inflammation-immunity)around these naughty and unstable cells might be fundamental, at least in the initial phases and later on, during the post-therapy so called remission phase.  Unfortunately, research in this context is lacking.
The whole interest seems to be on the bad cells themselves (blasts).
But we said before that the cause should be environmental...

endofpart1
(sorry I have to rush)
iko
« Last Edit: 11/08/2006 22:15:01 by iko »
 

another_someone

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Re: Does A Cell have the complete picture ?
« Reply #9 on: 10/08/2006 01:01:38 »
quote:
Originally posted by Carol-A
The environment of a cell will decide which genes are switched on or off. There has been a lot of work done on this, and it really is amazing! One are that is being ecplored is which genes are switched on and off to make teeth..... it would be useful to be able to regrow teeth. They now know which genes need to be switched on and off... even the difference between molars and canines. Some of this research came out of a study of certain cancers, where, for example, it has been observed in some ovarian teratomas (sp), teeth will actually grow. Anyway, although our DNA contains all the information, as it were, which bit is switched on where is largely due to position.



Is it really appropriate to talk about the environment of the cell, or are we really talking about the environment of the DNA?

Yes, it is true that some of the environment of the DNA is a consequence of the environment of the cell in totality, but no doubt there are some aspects of the environment of the cell that are never felt by the DNA, but more significantly, the environment of the DNA includes changes that go on within the cell that are themselves not directly related to anything outside of the cell (e.g. the DNA may cause a protein to be manufactured within the cell, that then becomes a part of the internal environment of the cell, that then triggers a switch elsewhere within the DNA this has nothing to do with anything outside of the cell, and is a totally contained mechanism wholly within the cell itself)?

This leads to the second issue that whether external or internal to the cell, is it not so that the dominant part of the environment of the DNA is itself initiated by the DNA itself (thus predominantly the decoding of the DNA is a cascade event, where the DNA is in essence stepped through by various paths as if it were decoding a computer program)?



George
 

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Re: Does A Cell have the complete picture ?
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