- #1
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Why is the DNA in eukaryotes an open ended string rather than a closed loop?
DNA in Eukaryotes: Open Ended Strings vs Closed Loops
- Thread starter arildno
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Discussion Overview
The discussion revolves around the structural differences between DNA in eukaryotes and prokaryotes, specifically focusing on why eukaryotic DNA is typically linear (open-ended) rather than circular (closed loop). The scope includes evolutionary biology, genetics, and the implications of DNA structure on organism complexity and reproduction.
Discussion Character
- Exploratory, Debate/contested, Conceptual clarification
Main Points Raised
- Some participants suggest that the linear form of eukaryotic DNA may facilitate the development of more complex organisms and ecological niches.
- Others argue that the length of DNA is not the primary reason for its linear structure, noting that many bacteria have large genomes with circular DNA.
- One participant proposes that the evolution of linear chromosomes in eukaryotes may be linked to the acquisition of stabilizing genes, while also highlighting the advantages of linear DNA for sexual reproduction and recombination.
- There is a suggestion that circular DNA may not support the same level of genetic mixing during meiosis as linear DNA does.
- A participant raises a question about the evolutionary timeline of the transition from circular to linear DNA, indicating a potential area of exploration.
Areas of Agreement / Disagreement
Participants express differing views on the reasons behind the structural differences in DNA, with no consensus reached on the primary factors influencing the evolution of linear versus circular DNA.
Contextual Notes
Some claims about the stability of linear chromosomes and their role in sexual reproduction remain unverified within the discussion. The evolutionary implications of DNA structure are also not fully explored, leaving several assumptions unaddressed.
- #2
spuriousmonkey
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because it is too long to be in a loop?
- #3
Monique
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..something with D-branes.. I don't remember 
But seriously, it is a good question.. let's turn it around: why is the DNA in prokaryotes circular and when did the separation between circular and linear DNA start. I guess spuriousmonkey has a point.
But seriously, it is a good question.. let's turn it around: why is the DNA in prokaryotes circular and when did the separation between circular and linear DNA start. I guess spuriousmonkey has a point.
- #4
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This is how I think about it:
that by using an open ended string form, it is easier to build up
a more complex organism which might carve out new ecological niches for themselves.
But since this is wild, unsubstantiated speculation from my side, I wanted to hear an expert's view on the matter..
that by using an open ended string form, it is easier to build up
a more complex organism which might carve out new ecological niches for themselves.
But since this is wild, unsubstantiated speculation from my side, I wanted to hear an expert's view on the matter..
- #5
iansmith
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I don't think it is a question of length. Many bacteria have more than one chromosome and if you add all the genetic material (including plasmid) some bacteria have large genome. Linear chromsome tend to be unstable if some component are not present. Circular chromosome can be done artificially in yeast (http://www.nature.com/cgi-taf/DynaPage.taf?file=/ng/journal/v20/n2/abs/ng1098_203.html)
I think the difference between linear and circular is probably due to their distinct evolution and early in their evolution, eukaryotes acquire genes that stabilize the linear form. As far as complexity and exploting unique niche, bacteria are ahead of eukaryotes. Linear chromsome seems better suite for sexual reproduction. Recombination between two linear chromosome seem to be easier than circular DNA.
This is paper on the evolution of linear chromosome in bacteria.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T2W-405SX5F-1&_user=458507&_handle=B-WA-A-A-BW-MsSAYZW-UUA-AUYZAZDVBE-AUYBDVYWBE-BEBWEBBUY-BW-U&_fmt=summary&_coverDate=05%2F05%2F2000&_rdoc=1&_orig=browse&_srch=%23toc%234929%232000%23998139997%23192052!&_cdi=4929&view=c&_acct=C000022002&_version=1&_urlVersion=0&_userid=458507&md5=66cbcaff630244073273ac3dca1eed2f
I think the difference between linear and circular is probably due to their distinct evolution and early in their evolution, eukaryotes acquire genes that stabilize the linear form. As far as complexity and exploting unique niche, bacteria are ahead of eukaryotes. Linear chromsome seems better suite for sexual reproduction. Recombination between two linear chromosome seem to be easier than circular DNA.
This is paper on the evolution of linear chromosome in bacteria.
http://www.sciencedirect.com/science?_ob=ArticleURL&_udi=B6T2W-405SX5F-1&_user=458507&_handle=B-WA-A-A-BW-MsSAYZW-UUA-AUYZAZDVBE-AUYBDVYWBE-BEBWEBBUY-BW-U&_fmt=summary&_coverDate=05%2F05%2F2000&_rdoc=1&_orig=browse&_srch=%23toc%234929%232000%23998139997%23192052!&_cdi=4929&view=c&_acct=C000022002&_version=1&_urlVersion=0&_userid=458507&md5=66cbcaff630244073273ac3dca1eed2f
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- #6
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iansmith, great!
So, linear DNA is the best tool for gene-mixing when gene-mixing is to occur by means of sexual reproduction?
So, linear DNA is the best tool for gene-mixing when gene-mixing is to occur by means of sexual reproduction?
- #7
Monique
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I think he has a very good point too.. on average 40 cross-overs occur during meiosis, I don't see that happening with circular DNA.. :)
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