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Diploid meiosis and crossover

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Diploid meiosis and crossover

Postby M0381U5 » Sun Aug 31, 2008 5:03 am

Could the Crossover stage in the formation of a zygote in the process of a haploid cell being generated from a diploid cell in the process of sexual reproduction be considered a Programmed Mutation, is the crossover stage completely random, and the billions of possbile offspring generated by the same parents, be considered mutations??? or is there an underlying algorith the allows different offspring to develop
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Postby alextemplet » Sun Aug 31, 2008 1:39 pm

I'm not exactly sure, but I wouldn't consider it to be mutation because crossover only randomly mixes the genes to determine which gamete gets which genes. Mutation, in my opinion, deals with actually altering the genes and not just mixing them together.
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Re: Diploid meiosis and crossover

Postby Darby » Sun Aug 31, 2008 6:39 pm

Any change in DNA at any level is technically a mutation - crossing over should count anyway, since it separates and recombines alleles and "changes the mix."
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Re: Diploid meiosis and crossover

Postby M0381U5 » Mon Sep 01, 2008 3:06 am

This is what conclusion i came to as well.
I searched for the definition of genetic mutation, and did not find any information that clearly stated how the crossover process is classified as far as genetic diversity is concerned.

Obviously the Error in replication from chemical, radiological or other means of interference are considered a Mutation, but weather the crossover stage is actually a mutation needs to be clarified, if it isnt already. if anyone has a link to research or information that may shed light of this classification, it would be most appreciated.
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Re: Diploid meiosis and crossover

Postby bio0325 » Thu Nov 06, 2008 5:39 pm

As far as I'm aware, a genetic change is only considered a mutation if it is not fixed prior to replication. In other words, it's only a mutation if the DNA replicates with the change. Because crossover happens after replication, I don't think it is technically considered a mutation.
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Postby M0381U5 » Fri Nov 07, 2008 4:04 am

The purpose of sexual reproduction and cross over is to create diversity. Diversity is neccessary for adaptation. So sexual reproduction is a type of controled mutation, not so much accidental.
Im not sure the best way to express my thinking is, but i feel that crossover is in a sense a kind of mutation.
I have postulated an idea that i hoped would be explained or determined in this forum, but responses are few and far between.
If anyone know of any more popular forums please let me know
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Re: Diploid meiosis and crossover

Postby wbla3335 » Fri Nov 07, 2008 5:57 am

I think the problem is due to the lack of precise, universaslly accepted definitions in biology. Look up "mutation" in 5 different biology or genetics dictionaries and you'll get 5 different definitions. Common usages of this word are often grossly limited to something bad that causes disease (mostly the human medical community guilty here). My own view, which is no more than my own view, is that recombination should not be considered as mutation but as part of the normal process of meiosis, something that generates polymorphism within gametes. Is intron splicing mutation? To me, no.

As far as other forums go, maybe you could try the Genetics forum of Biology Online or the BioForum forums (http://www.protocol-online.org/forums/i ... 8a0e682e2&). BioTechniques also has taken over a set of biology forums (http://molecularbiology.forums.biotechn ... 9f9e888604) but are mostly methods oriented.
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Postby Darby » Fri Nov 07, 2008 10:51 pm

Crossover change is a mutation because the exchanges are often unequal - genes are lost or gained from these. Those DNA changes, if passed to offspring, are replicable mutations. This is where additional genetic information comes from, allowing mutational changes in existing genes without losing original functions - bigtime player in evolutionary change.
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Postby MrMistery » Sat Nov 08, 2008 4:14 am

gene conversion....
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Re: Diploid meiosis and crossover

Postby wbla3335 » Sat Nov 08, 2008 8:11 am

Recombination is a normal, programmed process that most eukaryotes undergo. Unequal crossing over and gene conversion are rare variants on the theme that lead to polymorphic states outside the recombinatorial norm. Including these events as mutational is quite valid. If you want to define mutation as any change to a genome or its products, then this would include recombination, amongst a host of other programmed processes (eg. intron splicing). Again, it comes down to what definition you accept for the term mutation, and I doubt we will settle the issue here. Personally, I'm just uncomfortable with calling programmed processes errors, which are what mutations, for me, represent.
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Postby MrMistery » Sun Nov 09, 2008 9:05 pm

intron splicing does not alter DNA sequence, so leave it out...
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