Re: cell life cycle

[Jerry Zhu <***>]

Steve,

I go with your memory about 97% of human DNA.

My suggestion is that ancestor of human such as mouse
have less % of junck DNA according to atavism.

I wounder if we can physically remove the junck DNA
start from mouse and eventually human and see what
happens 

Jerry

--- Steve Johnson <***> wrote:

> 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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