|
Register | Sign In |
|
QuickSearch
Thread ▼ Details |
Member (Idle past 5596 days) Posts: 239 From: Upper Portion, Left Coast, United States Joined: |
|
Thread Info
|
|
|
Author | Topic: Problems with Chromosomal Evolution - From Circular to Linear | |||||||||||||||||||||
Ooook! Member (Idle past 5815 days) Posts: 340 From: London, UK Joined: |
I realise that it does nothing to really tackle the main point of the OP, but I do think it changes the nature of the challenge slightly. If the nucleus evolved from a parasitic or symbiotic organism that had a linear chromosome (in other words never made the transition to circular) then the chain of events stops being:
Linear => Circular => Linear (which seems like a wierd way of going about things) to Linear => Circular and Linear Parasitic organisms would get around the problem of chromosome stabilisation by replicating like mad and using the host to keep their genomes relatively small, whilst others developed circular chromsomes to become all-singing all-dancing biochemical factories. It removes the absolute requirement for telomeres to survive, and presents the possiblity that parts of the hosts genome could be co-opted by the parasitic DNA to stabilise the ends of the relatively unstable linear chromosome (I think this is what Loudmouth was saying). As for what the abstract said about the chain of events, I think I could sum it up like this:
This cell-turned-predator idea would also explain the advent of mitochondria and chloroplasts (but that is Off-topic) Concerning the new topic suggestion: I certainly like the idea of a thread entitled 'All men are parasites' (or similar), but I'm afraid I don't know too much about the evolution of sex so I might have to do a bit of digging or turn it into more of an enquiry type of topic - unless you want to have a shot at it of course.
|
|||||||||||||||||||||
RAZD Member (Idle past 1404 days) Posts: 20714 From: the other end of the sidewalk Joined: |
It may well be that the original linear system was very inefficient and subject to frequent breakdown. It may even have been a not-quite-life system of chemical reactions that sometimes succeeded.
The issue of mitochondria and chloroplasts also speaks to the actual mechanism if one theory can explain them and the linear chromosome concerns (that occam flashing blade thingy) Men as parasites or viruses -- they inject DNA into the host and coopt their reproduction mechanism to make a copy .... heh we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
|
|||||||||||||||||||||
Peter Member (Idle past 1478 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
If there was some "organism" several steps back from
both, that branched over a number of change cycles to result in both types of cell then the link between the types would be further removed and less of a conundrum. What makes prokaryotic cells more primitive, BTW?
|
|||||||||||||||||||||
Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
If there was some "organism" several steps back from both, that branched over a number of change cycles to result in both types of cell then the link between the types would be further removed and less of a conundrum. I don't see how that neccessarily follows. In that case you would have to be able to characterise your hypothetical common ancestor to show that it wasn't either pro- or eu- karyotic. And since being pro- or eu- karyotic basically depends on whether or not the cell has a nucleus, ther isn't much room for some in between sort of common ancestor. Why do you think your scenario is any less of a 'conundrum' than the eukaryotes being a divergent population from a prokaryotic base.
What makes prokaryotic cells more primitive, BTW? A couple of answers to this, firstly because prokaryotes are the very first things in the fossil record. The first fossil evidence of life is of stromatolite cyanobacteria, the prokaryotes precede the eukaryotes by a couple of billion years. The second is the reason I previously mentioned, if the nucleus is the result of endosymbiosis then the original engulfing host cell must have lacked a nucleus and would therefore be prokaryotic by definition. TTFN, WK
|
|||||||||||||||||||||
Peter Member (Idle past 1478 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
ther isn't much room for some in between sort of common ancestor. I wasn't thinking of 'in-between' when I was thinking of commonancestor, rather more like enabling the development of either -- which really isn't the same -- honest Why do you think your scenario is any less of a 'conundrum' I was thinking more scope for changes to become manifest insmaller steps ... in reference to this DNA structure comment someone raised. the prokaryotes precede the eukaryotes by a couple of billion years So by 'more primitive' you just meant older?
|
|||||||||||||||||||||
Wounded King Member Posts: 4149 From: Cincinnati, Ohio, USA Joined: |
So by 'more primitive' you just meant older? Not just older. Also 'primitive' as opposed to 'derived', eukaryotes are a form of life derived from the prokaryotes. Primitve as in little evolved from or characteristic of an earlier ancestral type. My point has been that that ancestral type, the common ancestor of modern prokaryotes and eukaryotes, would have been a prokaryote. If you want to find the first common ancestor which wasn't a prokaryotic cell then you have to go to pre-cellular life. The first cell surely had to be a prokaryote (without a nucleus) but it didn't have to be a modern prokaryote. TTFN, WK
|
|||||||||||||||||||||
Peter Member (Idle past 1478 days) Posts: 2161 From: Cambridgeshire, UK. Joined: |
That works for me
|
|||||||||||||||||||||
jt Member (Idle past 5596 days) Posts: 239 From: Upper Portion, Left Coast, United States Joined: |
Hey guys,
Sorry for taking so long to respond - I'm very busy with school (I'm taking calc 2, physics, and chemistry, in addition to tutoring part time in the math lab), and I probably won't have enough time to respond the posts in this thread until a big, long break. Actually, I don't have enough time to participate in any thread which requires research, which means pretty much none of the science threads. (Loudmouth, if you read this, I saw your HERVs thread - very well written, and that is one of the arguments that currently has me stumped. I want to learn more about it and discuss/debate it with you, and I will when I have the time) Just wanted to let y'all know that I didn't bug off into outer space or anything. JT This message has been edited by JT, 10-19-2004 11:38 PM
|
|||||||||||||||||||||
NosyNed Member Posts: 8996 From: Canada Joined: |
You mean, gasp!!, you have a life??
|
|||||||||||||||||||||
jt Member (Idle past 5596 days) Posts: 239 From: Upper Portion, Left Coast, United States Joined: |
Aside of here, yes. Aside of school, only a little.
|
|||||||||||||||||||||
pink sasquatch Member (Idle past 6022 days) Posts: 1567 Joined: |
Hey JT,
I just "back into town" myself - if you feel there are loose ends in this thread you still want to discuss, let me know... Good luck on your course load - remember that physics is really just math, and chemistry is really just physics, and biology is really just chemistry - so you really only have to study calc and the rest will follow... (please don't actually follow this as practical advice, though it was given to me by a professor once... and has some degree of truth to it...) good luck
|
|||||||||||||||||||||
jt Member (Idle past 5596 days) Posts: 239 From: Upper Portion, Left Coast, United States Joined: |
I just "back into town" myself - if you feel there are loose ends in this thread you still want to discuss, let me know... I still want to discuss the potential for t-loops to have been the evolutionary bridge between circular and linear chromosomes. When I get the time I'll definitely be tying that up (hopefully by clearly emerging as victor - possibly by winding up the loser - of this debate). Very good advice - almost.
|
|||||||||||||||||||||
RAZD Member (Idle past 1404 days) Posts: 20714 From: the other end of the sidewalk Joined: |
welcome back. looking forward to more.
we are limited in our ability to understand by our ability to understand RebelAAmerican.Zen[Deist
{{{Buddha walks off laughing with joy}}}
|
|
|
Do Nothing Button
Copyright 2001-2023 by EvC Forum, All Rights Reserved
Version 4.2
Innovative software from Qwixotic © 2024