Kachana

Thanks for the replies.

I ask as I made the the following argument to a pro-lifer. He maintained that, in principle, something that WILL eventually become a human (i.e., a fertilised egg) should be valued as though it were human, therefore not aborted.

I made a few arguments, including that if a scientist with the right technology had had a human cheek cell and the right conditions to clone the cell, that destrotying the single cheek cell would be murder (or wrong or whatever) as it too would be on course to becooming human.

There seem to be conflicting answers so I'm not quite sure what to think right now, Basically, is human cloning ever likely, in the future, to be acheived with the bypassing of the fertilised egg stage where many pro-lifers say human life begins?

MyKell

Kachana,
No one said anything about a fertilized egg. We were talking about an empty ovum. The cytoplasm of an ovum contains a gradient of RNA molecules which are translated to produce a gradient of proteins upon fertilization. This, in turn, is the initial step in asymmetric cell division, which is the basis of multicellular ontogeny. The process of insertion of a diploid nucleus inside the ovum bypasses fertilization, and thus starts embryogenisis.
The destruction of an epithelial cell is, arguably, not murder.

Kachana

Cheers, I got confused there. Looks like my argument is salvageable!

pz

There is also highly specific information present in the cytoplasm/membrane, and the environment of the egg in general. It's simply much harder to analyze than the localized and codified information in the nucleus, so you tend not to hear much about it -- but it's there.

It will be easier to use 'advanced technology' to synthesize a genome from sequence information, and skip the entire epithelial cell contribution altogether, than to build a synthetic ovum. We don't even know where to begin on the latter problem.

theyeti

I might be wrong, but I think what pz is referring to (at least in part) are maternal effect genes whose products are necessary for embryonic development. Stored mRNAs for example contain highly specific information that won't be found in a cheek cell. (Maybe you could alter a cheek cell to get it to express some of those genes, but then it wouldn't really be a cheek cell any more.) I know that Drosophila has such stored mRNAs, but I'm not sure about humans.

theyeti

pz

Of course we do! Just what do you think is in those gigantic ova?

But it is more than that -- it's a mistake to reduce it to just genes. The ovum has a very elaborate structure that is defined epigenetically. We aren't even close to being able to assemble all the intricacies of that extranuclear stuff, even though we've got a pretty good idea about how to synthesize genomic information.

doghouse

Yes, Dolly the sheep was cloned by combining an oocyte from which the nucleus had been removed with mammary cells grown in cell culture.

He's right. ... that obviously explains why human mammary tissue is so highly valued.

Valmorian

There's no need to resort to cloning if you're taking this angle. Simply point out that every time a woman or man chooses to abstain from potential sex, they are also interfering with the 'right conditions' to form a baby.

Valentine Pontifex

Re: Is the info there.

PZ, a question for clarification.


Okay the epithelial cells don't have all the non-genetic structures and appropriate genes activated. But I would think that it is a safe assumption that the cloners have access to such material from other sources i.e. appropriate cells from another individual. Then the genome of that appropriate cell can be replaced with the genetic material obtained from the cheek cell.

Of course that is, I am sure, well beyond current abilities. But is there any reason why that could not be done in the future if the people in the future wished to?

Of course it would not be an "exact" copy of the cloned person if only because enviromental effects. How much difference would having different starting membranes have?

Kachana

Yup, I made a similar argument to this also, saying that a condom could be considered murder by the principle he posited since it too would interfere with what would eventually result in a human life.

He came back with a probabilistic argument to the effect that the set of the sperm and an egg is less likely than a fertilised egg to result in a human. I replied that such reasoning A) mandates a specific percentage cut off point at which the likelihood of a child is low enough to make a condom acceptable since it's "not very likely anyway," how does one choose this cut off point? B) Implies that if woman A, who has a fertilized egg inside her, has X% chance of producing a live baby, whereas woman B, who has sperm and an unfertilized egg inside her, has >X% chance of producing a live baby (the difference could be due to age/health concerns) then it is worse for the woman B to use contraception than it is for woman A to abort her fertilized egg, and C) that if future fertility technology raises the probability that sex will result in a baby to comporable levels exhibited now by an already fertilised egg, then condoms would become murder, simply as a function of technological advances.

Anyway, I'd better shut up before this gets booted to the morality forum!