This space race ....

[fitzley]

Excellent! (+)

I remember him mentioning how busy he was the last time he resurfaced.

[wames2]

DNA is a bit of tricky thing.  Hello All, sorry for my extended lapse.  I've two undergraduate degrees to finish, a student organization to run, and other varied time leeching activities.

Now, to the point.

The actual replication of DNA is very conservative process: the original code is maintained with extremely high fidelity, such that resulting copies are (ideally) identical the original.  The actual process is called semiconservative replication, as the new copies are formed with an original helix unwinds and a new complementary strand forms to zip each side up.

The introduction of genetic diversity, recombination, is a whole different story.  There are a few different metaphors one could throw at the alien's genome, but in this case I'll use a virus.  A virus takes control a host's cellular functions to replicate its own DNA, but often recombines with the host's genome, yielding a genetic change.  In replication, only the original viral DNA is copied.  In recombination, some form genetic exchange has occurred from the interaction of the two genomes.

Presumably, the Alien's genome is set up for at least some kind of recombinatory practice prior to the process of gestation and maturation.  Off the top of my head, I can speculate a bit of the actual genomic means this would occur within the cell.  When I speak of alien genome, I'm describing what is introduced into the host, not the final product.  My immediate thoughts on mechanisms:

Complete recombination.  The wanton exchange of any homologous genetic bits with the host's genome.  The Alien's genome is comprised of a slew of pocked genes with sticky ends that cut out and snatch up matching segments of the host's genome.  Afterwards, alien proteins reform the sparse segments into a proper structure, likely a collection of linear chromosomes.  This model requires a great deal of integrity with the parts involved.  There are many places where even a slight mistake by the myriad mechanisms driving such a process would cause catastrophic failure.  This model also fails to take advantage of a possible transformation of the hosts cells.

Transposon Driven Recombination.  Here, the alien DNA is a collection of "jumping genes" which activate upon insertion into host cells and find particular sequences within the hose genome to insert, replicate, and jump out.  Presumably, a diverse enough collection of properly aligned transposons could entirely reshape the host genome by inserting  into areas and transforming them into the required genes.  This method is a bit nebulous, but is very hardy as its distributed nature makes it damn near impossible to stop.  However, it would also be painfully slow, as transposons behave in a somewhat random manner.  Control and direction of the transformed cells might be accomplished via products resulting from genetic changes.

Primed Replication and RNA driven recombination: In this scenario, the alien genome is a massive collection replication promoting proteins and small initiation segments called primers.  Each primer is hybrid helix, consiting a strand of DNA and a complementary strand of RNA .  When the strand of DNA is ready for replication, the complementary RNA disengages and performs some catalytic function, in this case locating and sniping out a similar sequence in the host genome.  After the DNA portion of these many, many primers are replicated to proper quantities, hijacked host proteins patch these fragments together with the snipped out portions of the host genome.  The end results are alien chromosomes and a huge aggregate of active alien RNA.  At this point, these components completely decimate any remaining host genetic material and proceed with cellular transformation.

Please keep in mind that these are completely ad hoc thoughts, and as such do not have the rigor of scientific examination.  Basically, they could be complete wash, but at the moment they seem reasonable.  I'll post a bit later with some additional thoughts on the topic.

[Thedus]

 

[NERMAL]

+ for Wames (AzureFromage )

I like to think the two methods of procreation complement each other and co exist.

Firstly the morphing. This would dilute the creatures genome from generation to generation. Might even have been evidenced by the dog alien not needing pipes because as a second generation creature it was adapted to an oxygenated environment. Who knows?

Then there's the queen. The genetic failsafe. Aliens spawned from eggs layed beget a version closer to its real form than those from morphed hosts. Even the expulsion of the Newborn, the sum total of human DNA in its system, lends credence to the idea. In the absence of the matriarch, one of the crossbreeds could molt. Its been mentioned before...

[wames2]

The Queen's role as a genetic bastion is certainly consistent in what is seen here on terra firma.  Take Eusocial insects, such as honey bees.  While each daughter has the potential to produce eggs, the queens phermonal cues (normally) prevent this from taking place.  The centralization of reproduction to one individual allows for a vast population that is also genetically conservative, preserving the overall character of the hive in the mold of the queen. 

The production of the eggs within the alien may well be a form parthogenesis, an in vivo form of cloning found in a smattering of animals, notably a few lizards and sharks.  If the alien's method of development is consistent with my aforementioned viral metaphor, eggs then would be a nearly reversed process.  The source cells from the queen would undergo either extensive gene silencing or region expansion.  In the latter case, "pure alien" elements of the genome are copied to ludricously large quantities.  This is actually quite well seen in life, notably in tissues where a particular gene needs to be constantly expressed.  For example, regions of the human liver are made up of essentially tetraploid  cells--cells with twice the normal copies of parts of the genome.  This pales in comparison to the salvary cells of the fruit fly, which may have over 1000x the amount of a particular genome region!
In the case of the egg source cells, these expanded regions would extract themselves and join to form the effective genome of an egg.  Perhaps this new genome would bud off from the mothercell and then proceed unto development, eventually forming a complete egg and facehugger.  If this were the case, the pure alien elements of the genome could be preserved, allowing each egg to avoid complications due to posessing hybrid genetic material.

[fitzley]

Hey wames2...don't miss out on this conversation...

http://www.alienexperience.com//index.php?option=com_smf&Itemid=542&topic=3559.30

[deezelboy]

Ok, it's taken me about a week to digest what wames2 said (+) - much thanks!  Now, questions...

A) How does the Alien know which segments of DNA to pilfer from?  What I mean is, the large majority of DNA does nothing, only less than 10% code for proteins.

B) And of that 10%, how does the Alien know that certain segments produce the desired results? I mean, genes aren't exactly switches - some genes produce proteins whose only function seems to be to turn other genes on?

C) Would it be easier for the Alien to 'grow' a human foetus (albeit in somebody's chest) up to a certain point in development and then alter it?

[Thedus]

C) Would it be easier for the Alien to 'grow' a human foetus (albeit in somebody's chest) up to a certain point in development and then alter it?

I would think it would be easier to go the other way: grow an alien "fetus" ans then alter it. And considering the fact that the alien is always inherently "alien" - meaning that it pretty much retains a consistent appearance of the species with only relatively minor changes to certain gross anatomical features - it would seem more logical to start with alien and add a dash of host here and a sprinkle there.

The Newborn on the other hand may have followed the path of human fetus with alien genetic additives... sort of  a human chestburster in an alien host.

...Sorry, long week.  Not thinking very technically at the moment.

[[DX-ST]Peter]

But, the Aliens die easy, one bullet and they are dead. The DNA Code passes from generation to generation. But the aliens don't have the same reproducting system with humans, sharks and dogs...
They have a queen based reproduction, like bees. Only the queen passes it's genetic code to the facehugger, which passes it to the victim and finally to the embryo. They are like ants, like Hudson said in Aliens, everyone of them is coming from a facehugger, so from an egg. So what's laying the eggs? The queen. What controls the show? The queen. I agree with wames2. The DNA can change, or not. The alien DNA, passes from generation to generation? No. Why? Because the "crew" of the hive, queens servants, cant pass their DNA. Only the queen can pass her DNA Code. The queen in Alien: Resurrection passed the human DNA to the Newborn. So it was half human. Because the queen was a part human.

[Thedus]

But, the Aliens die easy, one bullet and they are dead.

Depends on what the round is.  Smart Gun, yes.  Pulse Rifle, yes. Standard issue side arm, not so.  How many rounds did Gorman unload at the alien entering the air duct at Hadley's Hope?  They didn't do diddly.  Vasquez needed to plant the barrel at point blank range before it did anything.

It wouldn't do the Queen any good to have minions that are easily slain.  The alien exoskeleton can tolerate small arms fire extreme differences in pressure as well as temperature.  In the words of Ash "making it one tough little son of a bitch."

The DNA Code passes from generation to generation. But the aliens don't have the same reproducting system with humans, sharks and dogs...
They have a queen based reproduction, like bees. Only the queen passes it's genetic code to the facehugger, which passes it to the victim and finally to the embryo. They are like ants, like Hudson said in Aliens, everyone of them is coming from a facehugger, so from an egg. So what's laying the eggs? The queen. What controls the show? The queen. I agree with wames2. The DNA can change, or not. The alien DNA, passes from generation to generation? No. Why? Because the "crew" of the hive, queens servants, cant pass their DNA. Only the queen can pass her DNA Code. The queen in Alien: Resurrection passed the human DNA to the Newborn. So it was half human. Because the queen was a part human.

Very true, but the embryo is acquiring genetic material from its host.  Whether it's passed on to future generations or not.  The alien on Fiorina acquired DNA from it's host (dog or ox, depending on the version you're watching).  The alien born of Scar in Antarctica acquired Predator DNA.  This means that the aliens born of the colonists on LV-426, as well as Kane, had acquired human DNA.

To further what Wames2 is saying about bees and genetic relatedness: lets look at bees, since this was the example.  A Queen bee has a 50% genetic relatedness to her offspring, and each offspring has a 75% genetic relatedness to its sister.  Making the general population of a hive a very closely related family.  The Queen suppresses the reproductive abilities of her offspring because a second queen would offer a break in the genetic relatedness of the colony by further watering down the overall genetic relation of the hive.  There's also the fact that it would introduce a conflict in unity in the hive.

In Wames2 theory the Queen alien is reproducing by genetically suppressing her own host's DNA while creating eggs so that the aliens within the hive would all have the same genetic relatedness to each other... as well as to their queen since they would all be acquiring the same amount of DNA from a host.  ...Actually the implications here are quite amazing.  This would mean  that every hive would have the same genetic relatedness - not only to the brood within the hive, but to other hives.  Whereas unlike with bees each queen has a 50% genetic relatedness to her mother, which means that the genetic relatedness of the species can diversify greatly in a short amount of time.  The aliens, however would show little to no diversification over time.

However, if we take egg-morphing into consideration would we be looking at the same genetic relatedness as the rest of the species, or a break in said line of relation since adult aliens do not reproduce in the same fashion as a Queen? Hmmm. 

[deezelboy]

...Actually the implications here are quite amazing.  This would mean  that every hive would have the same genetic relatedness - not only to the brood within the hive, but to other hives.  Whereas unlike with bees each queen has a 50% genetic relatedness to her mother, which means that the genetic relatedness of the species can diversify greatly in a short amount of time.  The aliens, however would show little to no diversification over time.

But wouldn't the host DNA of each Alien born represent much more genetic diversity than is implied by Trivers kin selection theory? 

I lack the terminology, so the explanation is gonna be labourious!  But here we go...

A queen bee shares only 50% of the DNA of her mother because the other 50% came from her father, who is at least a bee.  Queens thus have 100% bee DNA.  The 0.75 that Triviers et al postulated as a basis for kin selection refers to the shared expressions of the genes in the bee genotype.  To go suddenly anthropomorphic, that both my mother and I share brown eyes is a demonstration of the expression of a pigment gene that I inherited from her, but the pigment gene itself is a part of the human genome - all humans have it (or should do), but the expressions vary.

This is why I may only share 50% of my DNA with my mother, but as a human I share near 95% with chimpanzees.  I don't feel any kin selection pressures with chimpanzees because it's the shared expressions of those genes that count, rather than the genes themselves (after all, all the bees in the hive have the same genes, being bees, but inherit the way those genes are expressed from their parents).

Aliens don't seem to have sex, so their genes are presumably unchanged from one generation to the next - they're clones of each other.  But by stealing parts of a host's genes - not the expressions of those genes (e.g. brown/blue eyes) but the genes themselves (e.g. compound eyes/eyestalks) - they are much more diverse than the members of a bee colony.  If the split is 80/20 in favour of the Aliens (as the Strauses mentioned a while back - just an example!) then the Queen's progeny aren't going toi be affected by kin selection anymore than human beings feel kinship with chimps, dogs and cows, all of whom share over 80% of their genes with humans.

Alternatively, I've read you completely wrong and apologise!

[Thedus]

Alternatively, I've read you completely wrong and apologise!

LOL!  Do you know how often I read people completely wrong?  No need to apologize if you are.

Looking at Wames' theory the queen would be suppressing genes or genetic expressions that are present due to the host the queen was born from, or expanding genetic regions of the alien genome to compensate for and over ride the host DNA to aid in the creation of an egg/facehugger that is essentially carrying only the alien genome, and none from the queen's host, thereby allowing each generation of aliens to 'start fresh.'

Unless I'm reading it wrong, ( ) Wames2 is presenting a theory that goes beyond simple parthenogenesis.   There is still genetic diversity among animals that reproduce in such a way.  Each egg would essentially be equivalent to "the first," or the egg that started it all.  In this manner each facehugger could create an alien that carried the same percentage of the alien coding and the same percentage of host coding.

...Although this doesn't really explain Scott's comment about the alien in ALIEN being biomechanical because of the Jockey.  But perhaps it does.  If an alien born of a given host, captures prey, transforms them into an egg, and so on, that facehugger will not be born 'pure' as it would be if it were born from the queen.  It would be carrying with it portions of the host genome and transferring that on the next generation.

...am I just talking in circles? 

[deezelboy]

I dunno...  My brain's gonna start hurting soon!

Looking at Wames' theory the queen would be suppressing genes or genetic expressions that are present due to the host the queen was born from, or expanding genetic regions of the alien genome to compensate for and over ride the host DNA to aid in the creation of an egg/facehugger that is essentially carrying only the alien genome, and none from the queen's host, thereby allowing each generation of aliens to 'start fresh.'

I think there's adequate examples of this - the fact the QUeen's six-limbed, although it must have emerged from a human host, is a bit of a giveaway, as is the lack of change between the Eggs & facehuggers on the Derelict (presumably borne of something with a bit of Space Jockey in it) and those of the Atmosphere Processor (borne of something with a bit of human in it!).

So you have your core Alien genotype - this has genes for Eggs and facehuggers and all the Alien bits of the Alien (but probably not, because neither humans or dogs have dorsal exhaust pipes, but Human-Aliens do and Dog-Aliens don't, but this is only a bit of an aside, as I know what you're talking about!). 

In this manner each facehugger could create an alien that carried the same percentage of the alien coding and the same percentage of host coding.

Yes, but this wouldn't mirror the kin selection found in, say, the eusocial insects.  All bees will carry the same percentage of their mother's coding as their father's coding, as a straight 50/50 split just like us, but different hives of bees won't view each other as kin and form superhives because it's not the ratio that counts, but the individual expression of the genes within that ratio. 

Basically, if your father wasn't my father, I'm less likely to view you as my kin, and less likely to work together for a common cause, because I'll be helping your father's genes (or rather the expression of those genes) gain another generation at the expense of my father's genes doing so.  But if we share the same parents, we'll share maybe between 50% - 75% of our parents genes between us, which means if I help you there's a good chance that the genes I carry will make it to another generation, even if I don't produce offspring and you do. 

Each Alien has a certain ratio of genes they swipe from the host, but unless they swipe the exact same genes - which could only happen if they were incubating in cloned hosts - the degree of genetic diversity is going to far exceed that needed for kin selection. 

This isn't going to affect the Queen, because she's always churning out the same core phenotype, which never changes after each generation (how do they get round parasites and viruses, I wonder? would this be their major weakness?).  Kin selection can't be used to explain why Aliens cede reproductive rights over to the Queen, because on a genetic basis this is not a close knit family, its a loose collection of hybrids who share something in common - taht something being the core Alien genotype, or a proportion of it. 

[[DX-ST]Peter]

So, from what we said, we should get a conclusion.

(1) Every alien in a hive except the queen should have a 95% of DNA similarity.
(2) This DNA similarity is coming from the host. In earth, there would be much different hives due to    the difference of the indigenous life forms.
(3) In LV-426, there were no indigenous life forms but there were the colonists. So all the aliens would be same.
(4) The predalien is around 50% - 75% Alien.

And some more questions:

(1) What happens if a predalien molt into a  queen?
(2) Are the different hive-race aliens fighting each other?
(3) Are the predaliens a different species?
(4) How would be the 100% Pure aliens?
(5) If the queen chest-bursts from a Predator, will her eggs be different?
(6) In Alien: Resurrection the queen was 50% human. How would she be if she was 50% Predator?

[NERMAL]

And some more questions:

(1) What happens if a predalien molt into a  queen?
(2) Are the different hive-race aliens fighting each other?
(3) Are the predaliens a different species?
(4) How would be the 100% Pure aliens?
(5) If the queen chest-bursts from a Predator, will her eggs be different?
(6) In Alien: Resurrection the queen was 50% human. How would she be if she was 50% Predator?

1. I quit this series, delete my membership, crawl up into a convenient clock-tower...
2. Perhaps. Humans do it all the time...
3. Diffrent sub-species.
4. Non alcoholic Christians...?
5. I think not. I believe the Queen is the genetic reset button.
6. It wasnt 50% human. Ripley wasnt half Alien. They just shared traits...It would look like a Jamaican rasta-newborn.