Reverse Evolution Getting Closer

[PsychoticEpisode]

Interesting show on Discovery HD this afternoon. They were talking about and conducting experiments in reverse evolution, specifically aimed at the possibility of turning a bird back into its ancestral reptilian relative.

The biologists on the show were using a hit or miss method of, and I hope I get this right, injecting live bird embryos with proteins to turn on genes long since dormant. They managed to produce rudimentary teeth on emu fetuses and change the scales on a chicken's foot into primitive feathers. An expert on the show predicted that in about 50 years we should be able to produce a reptile from a bird's egg, not necessarily the exact duplicate of the ancient relative but something close.

I was wondering just what percentage of the genes on a strand of DNA are turned off for any creature? If there are turned off genes then what are they doing there in the first place? Does an evolving creature save all the genes it has gathered(?) over the millenia or does it discard some at times? If it saves genes it no longer uses then does DNA contain the blueprint for all of a creature's mutations over the centuries? One more, is it possible that we may be able to totally track the evolutionary path of some animals simply by using their own existing DNA?

Personally I would love to see if it will happen within the 50 year time frame. I think that if they can do such things in a lab that it will leave little doubt of the reality of evolution. I really don't know how anybody could watch that show and not believe evolution ever took place.

 

[Hercules Rockefeller]

The biologists on the show were using a hit or miss method of, and I hope I get this right, injecting live bird embryos with proteins to turn on genes long since dormant.

Hmmm, I don’t see how that would work. Are you sure the approach wasn’t a form of gene therapy? In other words, inject embryos with DNA encoding genes that would otherwise be dormant in a given tissue? My former research involved expressing genes in embryos. I used to introduce DNA into embryos that would direct the expression of a given gene in a specific tissue.

They managed to produce rudimentary teeth on emu fetuses and change the scales on a chicken's foot into primitive feathers. An expert on the show predicted that in about 50 years we should be able to produce a reptile from a bird's egg, not necessarily the exact duplicate of the ancient relative but something close.

That’s mega-interesting, but I see that prediction as mostly hype specifically made for the Discovery Channel. It’s definitely possible to modify the development of an embryo to a certain degree. But to revert it back to an ancestor organism, no.

I was wondering just what percentage of the genes on a strand of DNA are turned off for any creature?

In a multicellular organism, the majority of a cell’s genes are inactive as cells differentiate into specialised cells with specialised functions. Aside from necessary “housekeeping” genes (metabolism, DNA repair, organelle functioning etc) a cell generally expresses only the genes it needs for its function and silences the rest.

If there are turned off genes then what are they doing there in the first place?

Each cell contains the genome for that organism. ie. all the genes that are required by all the cells that the organism will eventually comprise. This is necessary because multicellular organisms (like humans for instance) begin as a single cell.

Does an evolving creature save all the genes it has gathered(?) over the millenia or does it discard some at times?

Genomes evolve and change over time. New genes are gained (via duplication of existing genes and subsequent mutation/modification), some genes are lost, and most genes are modified over time.

If it saves genes it no longer uses then does DNA contain the blueprint for all of a creature's mutations over the centuries?

Genomes respond to selective pressures. If there is a strong selective pressure for a gene to be retained without mutation, then it is retained with little or no mutation. Thus, some genes for vital cellular processes (such as DNA replication, ribosomal function, metabolism etc) are virtually unchanged from mammals to bacteria. If there is no strong selective pressure on a gene, it is free to accumulate mutations or be lost through evolution.

One more, is it possible that we may be able to totally track the evolutionary path of some animals simply by using their own existing DNA?

Yes, of course! You can compare DNA sequences of different organisms and place them on an evolutionary tree that shows their respective evolutionary relationships. It’s an entire field of genetics called phylogenetics.

I think that if they can do such things in a lab that it will leave little doubt of the reality of evolution.

There’s already no doubt of the reality of evolution.

I really don't know how anybody could watch that show and not believe evolution ever took place.

There’s no accounting for some people.

 

[Hercules Rockefeller]

For instance, here is the evolution of a gene called Runx. There are multiple versions of this gene in present day mammals and they are specifically expressed in somem tissues but not others. The present day Runx genes arose via duplication events and subsequent mutation of a single precursor gene (called Runt) in primitive ancestor organisms.

 

[PsychoticEpisode]

Hmmm, I don’t see how that would work. Are you sure the approach wasn’t a form of gene therapy? In other words, inject embryos with DNA encoding genes that would otherwise be dormant in a given tissue? My former research involved expressing genes in embryos. I used to introduce DNA into embryos that would direct the expression of a given gene in a specific tissue.

This is the show summary http://www.dailymail.co.uk/sciencetech/article-1026340/Jurassic-Park-comes-true-How-scientists-bringing-dinosaurs-life-help-humble-chicken.html

Let's say all this is possible. If so then why stop there, could we not go all the way back?

 

[Fraggle Rocker]

. . . . is it possible that we may be able to totally track the evolutionary path of some animals simply by using their own existing DNA?

Uh, I think we need a real biologist here, but I'm pretty sure that one of the major drivers of evolution is the loss and replacement of genes through mutation and bottlenecks.

The farther apart two species are phylogenetically, the fewer genes they have in common. That's just Genetics 101A. It's considered likely that all organisms on earth are descended from the same ancestor, so clearly none of them has the complete set of DNA from the original organism. Therefore it would be impossible to recreate that ancestor from its descendants' genes. Too many of them are missing from each descendant species.

 

[francois]

Uh, I think we need a real biologist here, but I'm pretty sure that one of the major drivers of evolution is the loss and replacement of genes through mutation and bottlenecks.

Right. I read that humans have the gene which at one point let us (well, our ancestors) synthesize vitamin C; however, when our ancestors started eating fruit that gene became invisible to natural selection and so mutations weathered it into uselessness.

Many of the old genes may be there, but I doubt they'd be in any useful kind of condition. But it may be possible to repair the old genes and guess what they used to do.

 

[Hercules Rockefeller]

Uh, I think we need a real biologist here.

What is that supposed to mean? Are you suggesting I’m not a real biologist?

but I'm pretty sure that one of the major drivers of evolution is the loss and replacement of genes through mutation and bottlenecks.

I would say that one of the major drivers of evolution is the gain of genes, not the loss of genes.

Many genes that are present as single copies in yeast/Drosophila/C.elegans are represented as multigene families in ‘higher’ organisms. ie. multiple versions of the same gene. Through evolution these organisms have acquired extra copies of genes through duplication events. This has introduced redundancy into the genome. This, in turn, has removed the functional constraints from many genes any allowed them to mutate into new and exiting genes that are not present in ancestor organisms.

An E.coli cell has few (if any) functionally redundant genes; a human has many.

 

[PsychoticEpisode]

Seeing how I'm the obvious choice for not knowing what I'm talking about I supposed it is incumbent on me to ask the stupid question . It's the entitlement of the uninformed to ask such a question.....

If dormant or switched off genes are saved by an organism's DNA throughout the evolutionary process then could it be possible that such genes comprise some of what is considered Junk DNA, the part of the genome that appears to have little or no use?

Secondly, as an reciprocating afterthought, could Junk DNA also include genes waiting to be turned on for the first time. IOW's an organism's next evolutionary step is already stored away in safe keeping. If so, could there be several such genes that respond to conditions requiring an adaptation just waiting for the opportunity.

Summarizing: could Junk DNA contain the genes of our ancestral past and the genes necessary for future adaptational requirements?

I suppose that if our DNA does all that then there is reason to believe that mutation is not caused by an outside agency but from within the cells themselves, constantly working to improve the organism's survival chances. Each strand of DNA containing an arsenal of genes, old & new, just in case.

 

[swivel]

Uh, I think we need a real biologist here, but I'm pretty sure that one of the major drivers of evolution is the loss and replacement of genes through mutation and bottlenecks.

It is more the variability of each gene's expression rather than its presence or absence. People make a big deal about us being 98.6% genetically identical to chimps, but the difference in which genes are expressed and how often makes all the difference in the world.

The few genes that differ make large changes by controlling how many of which proteins each sequence of DNA concocts. This is also why the efficacy of drugs varies wildly between human races that are nearly identical genetically. The small differences create incredible variety.

 

[iceaura]

It's considered likely that all organisms on earth are descended from the same ancestor, so clearly none of them has the complete set of DNA from the original organism. Therefore it would be impossible to recreate that ancestor from its descendants' genes

The conclusion doesn't follow, even from the exaggeration of the "loss" or replacement aspect of evolution. It is possible to learn a lot about - possible even deduce exactly - the structure of an ancestral genome without a complete copy extant anywhere.

 

[Hercules Rockefeller]

If dormant or switched off genes are saved by an organism's DNA throughout the evolutionary process then could it be possible that such genes comprise some of what is considered Junk DNA, the part of the genome that appears to have little or no use?

The article in question has given you the idea that modern organisms are carrying large numbers of “dormant genes” belonging to our evolutionary ancestors. There are no “dormant genomes” that can be “reactivated” in a way that will convert an extant organism into an extinct organism.

This happens all the time. Some scientists like to use the media to popularise and advertise their work. There is nothing wrong with that, especially if it’s great work. But this always leads to the same thing – grossly simplified science and over-exaggerated claims. When scientists talk to other scientists or submit their work for peer-reviewed publication they are not able to get away with making claims that they cannot substantiate with hard experimental evidence. But it’s not the same when talking to the media and in such circumstances it is not uncommon to see some scientists making claims that sound impressive but, in scientific reality, are never going to happen.

It is fact that we can make an embryo develop some ectopic morphological features. This comes about by directing the expression of genes at inappropriate times and places in the embryo. These features can resemble those of ancestor organisms. But turning a modern day bird into a dinosaur is pure science fiction.

 

[PsychoticEpisode]

The article in question has given you the idea that modern organisms are carrying large numbers of “dormant genes” belonging to our evolutionary ancestors. There are no “dormant genomes” that can be “reactivated” in a way that will convert an extant organism into an extinct organism.

It is fact that we can make an embryo develop some ectopic morphological features. This comes about by directing the expression of genes at inappropriate times and places in the embryo. These features can resemble those of ancestor organisms. But turning a modern day bird into a dinosaur is pure science fiction.

The biologists on the show never claimed that they would produce the exact ancestor. What they did say was that they will probably be able to one day create a reptile using reverse evolution techniques.

Dormant is my word. What the biologists frequently referred to was switched off genes. Probably two different things since dormant implies it is meant to reactivate at any time.

You're saying that none of this is possible but yet we are able to monkey around with genomes and invent new versions of the same organism, like square tomatoes. Can you explain the difference?