03-05-2005 02:57									#1
	apolyton biochemists and biologists: what is a holliday junction? Lose 30 kilos (of popups)

Wikipedia doesn't know, and no explanation is provided in the article I'm reading

context: dna double crossover molecules

	03-05-2005 02:59									#2
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Google knows all
http://engels.genetics.wisc.edu/Holliday/
http://www.sdsc.edu/journals/mbb/ruva.html
"The nature of structural changes in DNA neccessary to result in
homologous genetic recombination were layed out by Holliday in 1964,
and in subsequent years the crossover-structures were visualized by
electron microscopy. The actual conformation of a DNA crossover was
speculated to be a four-way-junction with separate DNA helices, or
with stacked helices in either a parallel or an antiparallel
orientation of the helices. The models had to allow for branch
migration, else no exchange of genetic material would happen.
Homologous genetic recombination is a highly dynamic process, in
contrast to X-ray crystallography relaying on static structures. So it
took to the end of the previous millenium to get an atomic detail view
of relevant structures..."
http://www.biologie.uni-hamburg.de/...iday/4wjdna.htm

	03-05-2005 03:00									#3
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uh.... yeah

	03-05-2005 03:00									#4
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ah thx

	03-05-2005 03:02									#5
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Beautiful thing the holliday junction.

	03-05-2005 03:02									#6
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During meosis, with two chromosomes becoming paired, DNA strands from the two chromosomes become interwinded at a cross-over point. Molecularly, the Holliday junction is where the combining happens - the place where the DNA strands cross each other.

	03-05-2005 03:03									#7
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don't read such confussing stuff kuci... who do you think you are?

	03-05-2005 03:12									#8
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oh ****

I'm reading "the flexibility of dna double crossover molecules", and I don't understand their procedure AT ALL - I mean, I understand "we added such-and-such", I just have no clue what it's all doing and why it works

	03-05-2005 18:32									#9
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quote: Originally posted by Japher don't read such confussing stuff kuci... who do you think you are?

He goes to a HS for smart people. My God, I won't be learning about that stuff for at least another year.

	03-05-2005 18:44									#10
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quote: Originally posted by Kuciwalker oh **** I'm reading "the flexibility of dna double crossover molecules", and I don't understand their procedure AT ALL - I mean, I understand "we added such-and-such", I just have no clue what it's all doing and why it works

nm, I figured out some of it and the rest is irrelevent

w00t teh presentation was finished and is w00tly

	03-05-2005 18:45									#11
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quote: Originally posted by Odin He goes to a HS for smart people. My God, I won't be learning about that stuff for at least another year.

You're one of those sissy zoology people Why would you ever study this stuff?

	03-05-2005 19:05									#12
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quote: Originally posted by Kuciwalker You're one of those sissy zoology people

Studying the origin of animal phyla is sissy to you?

	03-05-2005 19:43									#13
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Zoology
Microbiology

That is all.

	03-05-2005 19:53									#14
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Someone send the boy some porn!!!

	03-05-2005 19:55									#15
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oh and me too please

	03-05-2005 20:05									#16
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quote: Originally posted by Immortal Wombat Zoology Microbiology That is all.

Zoology:
Microbiology:
Paleontology:
Ecology:
Developmental Biology:
Evolutionary Biology:
Molecular Biology:
Biochemistry:


BIOLOGY PWNS ALL!!!

	03-05-2005 20:20									#17
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quote: Originally posted by Odin Studying the origin of animal phyla is sissy to you?

You need the biotech people to do that, since phylogenetic trees are built now using rRNA comparisons

	03-05-2005 20:56									#18
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quote: Originally posted by Kuciwalker You need the biotech people to do that, since phylogenetic trees are built now using rRNA comparisons

Thats overrated, you can get different trees with different methodologies, although it is helpful. *points to recent redraw of the tree for protostome invertabrates* But you should not jump to conclusions, like when some molecular phylogenists had the gall to put elephants, manatees, hyraxes, and aardvarks (which are ungulates, or hooved mammals) together with some African insectivores and put them as the sister group to all other placental mammals, without looking at the morphological evidence that clearly shows that all hooved mammals (including cetaceans) are a monophyletic group.

	03-05-2005 21:00									#19
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They were using paleontological evidence as well though. It makes for a nice theory, having all the african animals distinct.

	03-05-2005 21:09									#20
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quote: Originally posted by Odin Thats overrated, you can get different trees with different methodologies, although it is helpful. *points to recent redraw of the tree for protostome invertabrates* But you should not jump to conclusions, like when some molecular phylogenists had the gall to put elephants, manatees, hyraxes, and aardvarks (which are ungulates, or hooved mammals) together with some African insectivores and put them as the sister group to all other placental mammals, without looking at the morphological evidence that clearly shows that all hooved mammals (including cetaceans) are a monophyletic group.

Genetics trumpts morphological evidence.

	03-05-2005 21:14									#21
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quote: Originally posted by Odin But you should not jump to conclusions, like when some molecular phylogenists had the gall to put elephants, manatees, hyraxes, and aardvarks (which are ungulates, or hooved mammals) together with some African insectivores and put them as the sister group to all other placental mammals, without looking at the morphological evidence that clearly shows that all hooved mammals (including cetaceans) are a monophyletic group.

	03-05-2005 21:15									#22
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what about seahorses?

	03-05-2005 21:20									#23
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If you'd have said sea cows, that would have passed for a sensible question

	03-05-2005 21:23									#24
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Seahorse is crazy looking, and funny because the male carries the eggs and plays beitch once they are born

I heard that there is a type of crab that changes sexes through the course of it's life.

	03-05-2005 23:01									#25
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quote: Originally posted by Kuciwalker Genetics trumpts morphological evidence.

A lot of mistakes can be made. For example, adult haemoglobin is mostly made out of 2 similar protiens, alpha globin and beta globin, both decended from a common ancestral gene in a jawless fish in the Cambrian. because of that, My a-globin gene is more similar to a goldfish a-globin gene than my b-globin gene. these two genes are part of the globin gene family, and can mess up molecular phylogenies. say we have a gene family with three similar genes, a biologists decides to compare human gene 1 with goldfish gene 1 and cow gene 1, but if, because the members of the gene family are so similar, that the biologist pick the right gene from the human and the goldfish, but picks gene 3 for the cow, you will get a tree showing the cow outside of a human goldfish clade, obviously incorrect.

Protist phylogeny is a case in point. At fist, the morphological and mollecular phylogenies were very different, the only similarity between the two were a grouping made of animals and fungi. Today, the morphological phylogeny hasn't changed much, but the mollecular phylogeny has changed greatly, It is now very similar to the morphological phylogeny.