What came first: the chicken or the egg?

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valich

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CNN just posted an article stating that geneticists, philosophers and chicken farmers finally solved this age-old riddle stating that it was the egg, based on what they say is the fact the the embryo has the same DNA as the chicken. What about phenotype variation affecting gene mutation? Mutations can occur due to elements in our environment, such as toxic chemicals and radiation. Also, there was just an article in Science showing that inheritance is apartly due to RNA transfer, and not solely DNA.

"Put simply, the reason comes down to the fact that genetic material does not change during an animal's life. Therefore the first bird that evolved into what we would call a chicken, probably in prehistoric times, must have first existed as an embryo inside an egg. Professor John Brookfield, a specialist in evolutionary genetics at the University of Nottingham." http://www.cnn.com/2006/TECH/science/05/26/chicken.egg/index.html

I think they need to study emryology first, or coevolution, and how oviparous animals evolved. Fish and amphibians have soft eggs that evolved into reptilian dinosaurs then into aves with hard eggs. The amniotic egg is an adaptation that evolved to protect the zygote and the developing embryo from the environment.

"Stewart (1997) showed that the first amniotic eggs probably had a flexible outer membrane, and that a mineralized (but still flexible) outer membrane is a synapomorphy of reptiles. The heavily mineralized, hard shell is a synapomorphy of archosaurs (crocodiles and birds), and it also appeared at least three times in turtles, and a few times in squamates. This probably explains why the oldest known amniotic egg (Coyne, 1999) only dates from the Lower Triassic (220 My), whereas the oldest amniote dates from the Upper Carboniferous (310 My); the eggs of most (if not all) Paleozoic amniotes must have had a flexible, poorly mineralized or unmineralized outer membrane, and thus had a low fossilization potential (Laurin, Reisz & Girondot, 2000)." Source: http://tolweb.org/tree?group=Amniota&contgroup=Terrestrial_vertebrates
 
No it's not. The phenotype can affect the transmitted DNA through mutations caused by a number of environmental factors, including toxic chemicals and multi-source radiation. This is not nonsense.
 
You have things backwards, unless you are talking about proteins directly associated with DNA transcription and replication.
 
valich said:
No it's not. The phenotype can affect the transmitted DNA through mutations caused by a number of environmental factors, including toxic chemicals and multi-source radiation. This is not nonsense.
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This is nonsense.

Point 1: The phenotype represents the physical characteristics of an organism determined by the interaction of its genetic heritage and environmental factors.

Point 2: The phenotype is a consequence of the genes and the environment, not a cause of either.

Point 3:The phenotype can be changed as consequence of mutations, some of which may arise from environmental factors.

Point 4: Therefore the phenotype cannot change the genotype.

Point 5:The phenotype can effect behaviour, it cannot effect its internal genetic constitution. This is another way of stating point 4, or Idle Mind's succinct and accurate 'You have it backwards'.
 
Genotype interactions with the environment always influence the resulting phenotype, as does epistasis. What about cancer cells? Mutator phenotypes cause mutations within the mitochondrial DNA resulting in gene mutations.

Further, the affects of phenotype mutations that occurred after we dropped atomic bombs on Japan are still being transmitted through the resultant mutated genotype. The radiation caused phenotype and genotype mutations.

Also, what about retroviruses? I'm not sure, but the rules for transcription get reversed: RNA to DNA.

In the Fly Embryo RNAi Project embryo field images show the phenotype mutations of various genes: http://flyembryo.nhlbi.nih.gov/heart-mutant.asp

"In a startling exception to classical genetics, mice in a lab experiment have inherited an effect of an aberrant gene without inheriting the gene itself...new study indicates RNA produced the odd-sounding result. In this case the result was mice with distinctive white tail tips: http://www.msnbc.msn.com/id/12956292/
In last Thursday's issue of the journal Nature
 
Genotype interactions with the environment always influence the resulting phenotype
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This is mostly correct. However in the post before you stated the contrary.

The phenotype can affect the transmitted DNA through mutations
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This quote exemplifies quite aptly that you do not have the slightest idea what you copy/paste the whole time. If one does not know what a phenotype or a genotype is, one should at the very least read a little bit in a very very basic, maybe highschool text-book before trying to prevent posting such nonsense. Repeatedly, I might add.
Ophiolite has quite clearly given the definitions from which it is quite easily deducible why there are no phenotype mutations.
Read his post again. Slowly. Then go to the library and check the words that you did not understand.
 
The chicken and egg argument isn't actually about a chicken and an egg its a metaphor for examining the origins of all life.
 
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dude, the chicken came first. there is clear evidence that the first chicken was spewed out of a volcano in a plume of ash and lava. this chicken was covered in heat-resistant reptilian scales that allowed it to survive the high temperatures in the mouth of the volcano. after it landed on the ground yards away from the volcano, it laid the first chicken egg, from which hatched a similar looking chicken. this happened over and over again for 25 million years until the chicken eventually evolved to develop feathers and other recognizable modern chicken traits. it's all in the bible. it's actually mentioned in the koran too, so you know it's true. chicken came first. egg second. problem solved.

i should be president.
 
At first the riddle appears confusing, it all depends on how you look at it. Alright, the first known chicken came in the form of an egg so some say the egg came first, at this point the host of the certain egg must resemble a chicken so much that you can’t even tell the difference. So how do you know the exact point the first known "chicken" arrived? As far as I know evolution is an on going process and in fact the chicken may be evolving as we speak. Therefore claiming the egg came first, while is right by all observation, is mere approximation. The other side of the coin of "the egg came first" solidifies my first paragraph; surely a chicken's egg cannot lay itself and needs some sort of host regardless of its nature. Therefore by all means we say the chicken or chicken-like organism came first, as an egg and embryo needs warmth and food, which can only be supplied by a compatible host. Therefore claiming the chicken or chicken-like organism came first is right by approach not observation. As we know observations can fail you, but not when you derive a reasonable method or approach. Therefore the riddle is solved; the chicken came first by all approach. The egg is just a way for a chicken to replicate itself, and anything has to exist in the first place in order to replicate itself. To the artist the egg came first but to the engineer the chicken came first, to some it’s the representation that matters while to others it’s the idea beneath the representation.
 
Chatha

As you say, there must have been an animal resembling a chicken that laid and nurtured the agg, but if we accept that evolution occurs by mutation then we must assume that the first chicken proper and which was different to its host must have been born of the first egg that happened to contain it.
 
True and correct, I agree with that. I am also glad you mentioned "assumed". What exactly is the chicken "proper" ? We know a chicken has a beak, feathers, and a waddle, but what about an animal that has all that except a waddle? Or what about an animal that has all that but has both eyes in front and not the sides? See why the observation aspect alone is flawed and for the artist? I am not saying you are wrong, you are in fact right, but you have to also take in consideration that you are also approximating
 
Which came first, the Homo sapien or the baby homo sapien? Obviously the baby homo sapien came first by mutation but my problem is at what point on the evolution chart did we know we had a "proper" homo sapien? Can anyone help me? By definition puposes the baby came first but what about the idea behind the definition? I guess such is life and science
 
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"Phenotype" affects the genotype??

Eh??

As for whether or not the organism laying the first "chicken" was itself...chicken-like...or whatever...given that maternal environmental donations to the offspring could be limited after hatch (let's face it; chicks do get care but might get by with a lot less), evolutionary differentiation could proceed a lot faster. A freakish looking mammal might get dumped by its maternal parent and not survive (being reliant on the maternal parent) but an organism demanding less from the parent post-hatch or post-partum might well get by even if it was a fairly large leap from the parent's pheno. It might have to run, though.

Still, sharks and lots of other r-selected types don't provide maternal care, and yet they look pretty much the same now as they used to. But there are a lot of different species. Hmm. Am I sounding Goldschmidtian? I don't mean to.

Geoff
 
CharonZ said:
This is mostly correct. However in the post before you stated the contrary.

This quote exemplifies quite aptly that you do not have the slightest idea what you copy/paste the whole time. If one does not know what a phenotype or a genotype is, one should at the very least read a little bit in a very very basic, maybe highschool text-book before trying to prevent posting such nonsense. Repeatedly, I might add.
Ophiolite has quite clearly given the definitions from which it is quite easily deducible why there are no phenotype mutations.
Read his post again. Slowly. Then go to the library and check the words that you did not understand.
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CharonZ: What you posted is a condescending post and quite apparently you do not have the slightest idea of what I do and do not know. I am trying - as I always have been - to explore the limits of our understanding without being constrained or restrained by orthodox beliefs. You should respect this cavalier attempt to explore that which we do not yet know as certain and the unlimited bounds of knowledge yet to be known and explored.

I repeat, what about Retroviruses? RNA to DNA.

Of course I know the difference between a genotype and phenotype and the genetic code. What is it that YOU do not know? Need help? What do you keep searching for by trolling these forums? Do we not have an equal unbiased desire to learn the unknown?

The MBL Woods Hole is currently researching RNA-directed centrosome replication in clams. This is now a hot subject. Care to comment?

We have recent discovery of Eukaryote activity dating back to 2.2 bya from fossil escavations in the Doushantuo Formation in Southern China. Therefore we have Eukaryote activity existing well over 100 mya before the Cambrian explosion. Care to comment?

"The clam centrosome study, led by MBL summer investigator Mark Alliegro of Louisiana State University Health Sciences Center (LSUHSC), in collaboration with Mary Anne Alliegro of LSUHSC and Robert Palazzo, of Rensselaer Polytechnic Institute, detected five RNA sequences in clam eggs that appear to be unique to the centrosome. “The implications are broad and I expect there will be lively discussion on their meaning for topics from cell division to eukaryotic evolution...The findings are likely to spark debate among biologists who have contemplated how these organelles self replicate. Although the consensus is that centrosomes lack DNA, the question of whether they contain RNA has never been adequately answered. “The RNA question has always been controversial, but we couldn't close the door on it,” says Dr. Palazzo. “This is the first really good evidence that nucleic acid co-purifies with the centrosome, which means it is physically present.” ....Using a technique Dr. Palazzo developed at the MBL, the scientists were able to isolate relatively large quantities of clam centrosomes. Skills developed in Dr. Alliegro's laboratory were then used to extract a unique set of RNAs and demonstrate their association with centrosomes biochemically and in situ . “The next step will be to determine what role these RNAs might play in centrosome replication, the cell cycle, or the development of organisms.”"
http://www.mbl.edu/inside/what/news/press_releases/2006_pr_06_06.html
 
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