Re: cell life cycle

[Steve Johnson <***>]

JZ: I also read somewhere that only about 10% of DNA are
known of its use. Most are not known or find
inactive. Anyone can explain or point out the
reference? I got some ideas why the inactive DNAs are
there.

 

SJ: Actually if my memory does not fail me according to current state of the art about 97% of human DNA as official designated as "junk DNA". There are a couple of common explanations. One is that the junk DNA is an evolutionary atavism which used to be transcribed in the ancient predecessors of an organizm but at some poit ceased to be useful. Another theory is that junk DNA are essentially parasites, remnants of retroviruses and the like which are only there because they can fool the cellular machinery to replicate them. 

 

An important point to note that "junk DNA" is defined simply as DNA with no known function. Thus at least some of the junk DNA has a way of becoming non-junk as the research progresses.

 

Robert Rosen wrote extensively (Essays on Life Itself) cautioning bioligists against premature euphoria in identifying genes with phenotypic characteristics. He showed that Medellian and Molecular "genes" are most likely not equivalent. Recent research shows that he was right in this analysis as increasingly researchers find that some junk DNA is not really junk and even that some information coding for phenotypic characteristics "resides not in the genes but in the gaps". I'm not making this up - I posted a link to a scientific american article about this to the list a couple of months ago. 

 

And lastly, as always it all depends on the observer who decides what is "function". From the perspective of the provirus happily residing in your DNA it is certainly not junk :)

 

WARNING: I'm not a biologist so this may all be wrong.

 

- Steve

 

 

Jerry Zhu <***> wrote:

> Lately I was thinking about the process of aging. I
> read somewhere life span is determined by the # of
> chromosomes' splits. A Russian lady falled in sleep
> at 37 and waked up thirty years later with a
> appearance of 37. Her appearance changed into 60s in
> one year. When asleep, cells are still splitting and
> dying but the rate various. How cells split and die
> and how the rate changes during the entire life?
> Cancel occurs when the cells do not die. I seem find
> out some reasons why and how bacteria split and why
> bacteria and organism remain at certain size. 
>
> I also read somewhere that only about 10% of DNA are
> known of its use. Most are not known or find
> inactive. Anyone can explain or point out the
> reference? I got some ideas why the inactive DNAs are
> there.
>
> I am not a biologist by training. I guess that there
> are biologists in
>  this list and seek some education
> here. Really appreciate for help.
>
> Jerry Zhu
>
>
>
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