Crossing Over

[dwaxe]

In meiosis, crossing over occurs. How does the DNA in one chromosome "know" how to swap with the DNA of its chromosome's homologous complement?

That sounded a little confusing. I'll try to clear it up.

One piece of a chromosome is cut from one chromosome and swapped with the exactly corresponding piece (strand of DNA) of its homologous chromosome (one from one parent, one from the other). How does the DNA "know" where to go on the homologous chromosome?

 

[Neonanocyborgasm]

In meiosis, crossing over occurs. How does the DNA in one chromosome "know" how to swap with the DNA of its chromosome's homologous complement?

That sounded a little confusing. I'll try to clear it up.

One piece of a chromosome is cut from one chromosome and swapped with the exactly corresponding piece (strand of DNA) of its homologous chromosome (one from one parent, one from the other). How does the DNA "know" where to go on the homologous chromosome?

In doesn't know. Crossing over is an accident of meiosis. It is not intended as a means of random assortment.

 

[Perfection]

In doesn't know. Crossing over is an accident of meiosis. It is not intended as a means of random assortment.

If it's just an accident, then why is it so prevalent in Eukarya , and so good at recombination?

 

[Neonanocyborgasm]

If it's just an accident, then why is it so prevalent in Eukarya , and so good at recombination?

Because only Eukarya have linear chromosomes. Prokarya and archaea (AFAIK) have circular chromosomes.

 

[Perfection]

That doesn't answer my questions. It says why it isn't present in prokaryotes, but that's not what I was asking!

I don't believe that crossing over can be characterized as an accident.

 

[Neonanocyborgasm]

That doesn't answer my questions. It says why it isn't present in prokaryotes, but that's not what I was asking!

I don't believe that crossing over cannot be characterized as an accident.

So you believe that crossing over can be characterized as an accident.

 

[Perfection]

Typo Fixed.

Please respond to the fixed post.

 

[Neonanocyborgasm]

Typo Fixed.

Please respond to the fixed post.

I'm not aware of an active mechanism for crossing over. Perhaps if you could find some evidence of enzymes and such that would facilitate the process, I'd believe it.

 

[Perfection]

I don't find that particularly compelling. When a complex (and adaptive) biological process is seen (as I'd claim recombination is), I think the burden of proof falls onto the proclaimer of accidental-ness not the denier. I do not trust that meiosis just so happens to be very good at producing crossing over by pure accident.

A thought I have here, is that meiosis could well be the mechanism for crossing-over, and that it is exquisitely "engineered" to cause it to occur.

 

[PlutonianEmpire]

I thought for sure this thread would be about ghosts.

 

[Perfection]

Thank heavens it isn't, because it would be in the wrong forum!