13
$\begingroup$

This question is brought on by a Sci Fi novel I am thinking about writing. The plot device involves a colonist in charge of building a population on a new planet who loses his supply of embryos and so forth in the landing. With the artificial "wombs" intact, he populates the planet with clones of himself.

If he wanted to introduce enough variation (without making up new genes, only rearranging) in the population to allow them to be able to reproduce naturally without inbreeding problems, would he be able to? In particular, could he make a woman? Alternately, could a woman (without a Y chromosome) do the the inverse?

At the risk of introducing bias into the answers, the plot as it stands assumes he is a male and he CAN'T do any of the above and he is restricted to clones.

| improve this question | |
$\endgroup$
  • $\begingroup$ If they're clones they'd be pretty much identical. He might have better luck making induced pluripotent stem cells and deriving them as gametes, then making embryos. Still have the same genes as he did, but at least the recessive/dominant allele ratios might change and could get some females out of it. Why not get DNA from the dead embryos? $\endgroup$ – user137 Jan 16 '15 at 3:02
  • $\begingroup$ That's a cool idea with the pluripotent cells. Of course exact copies would be clones, the idea is that he could have technology for directly manipulating the genes, he just doesn't know any sequences that are not present in himself. Your point about the eggs can be easily explained away by a fire, but it makes be think of the point that there could be DNA from anyone else who was involved with the building or launching of the ship still aboard $\endgroup$ – wedstrom Jan 16 '15 at 3:10
  • 1
    $\begingroup$ And it wouldn't be hard to keep an electronic database of DNA sequences on a computer. $\endgroup$ – user137 Jan 16 '15 at 3:19
  • 2
    $\begingroup$ From a narrow, technical perspective, a man "contains" all the genes to "make" a woman (X-chromosome) while women lack the genes to "make" a man (a Y-chromosome). To actually make use of this is another question (for instance, producing gametes containing X & Y chromosomes), but for a SciFi novel this shouldn't be a problem. Epigenetic effects might also be an issue. $\endgroup$ – fileunderwater Jan 16 '15 at 8:35
  • 2
    $\begingroup$ Related: biology.stackexchange.com/questions/17410/… $\endgroup$ – anongoodnurse Jan 16 '15 at 9:04
9
$\begingroup$

This answer also involves some speculations as the question is about a good theoretical framework for a science fiction.

You can find in this post about how sperm can be used to produce embryonic stem cells. It would still require an oocyte for doing that.

The question now is- Can you produce oocytes from a male?

You may fuse two X bearing haploid spermatids to form a diploid cell with XX. This cell will also have mitochondria and ribosomes — seems like a decent candidate. Gametogenesis has not been shown to happen in-vitro. Moreover a zygote will need a lot more cytoplasmic resources that you can get from a fused spermatid.

Plus there are imprinting issues as already pointed out by Chris.

Conclusion: Next to impossible

For your question "Does a man contain all the genes needed to make a women": yes he has but does not have the biological machinery to do that (exclusive of the womb).

However if you choose to send a female astronaut for this mission then there may be some hope. As Chris said, there are problems with homotypic fusions because of imprinting issues. But with a supply of ova there can be other ways:

  • Make clones using SCNT: limitation is that there would be very little variability.
  • Erase imprinting marks and fuse two oocytes: This has not been done yet but this is possible. At this moment we have technology (still incipient for therapy grade), for targeted genome editing. The basic principle involves fusing a DNA-endonuclease with a sequence specific DNA Binding Domain (DBD). Examples include Zinc Finger Nuclease, TALENs and Crispr-Cas. This study demonstrates an engineered system that can deaminate RNA in a sequence specific manner. Based on a similar principle it should be possible to link DNA-(cytosine/adenine)- methyltransferase or DNA-(cytosine/adenine)-demethylase to a sequence specific DBD 1. This system can be used for targeted epigenetic modification. This would have a little more variation than cloning because of meiotic recombination. Limitation is that there won't be any males, this would perhaps become an Amazonian Planet.

Make sure that your space-shuttle has a good biolab facility :P

1 Imprinting is generally implemented by DNA methylation which happens mostly on cytosines.

| improve this answer | |
$\endgroup$
  • $\begingroup$ Thanks guys! All your answers have contributed a fascinating and realistic backdrop with which to write! $\endgroup$ – wedstrom Jan 28 '15 at 0:22
8
$\begingroup$

A woman (assuming no mosaicism) has two X chromosomes in the nuclei of her cells (except for oocytes). A man, in every cell with a nucleus (except for spermatocytes), has only one, pluripotent or not.

The only way he could make a female would be to either manipulate cells by duplicating the X chromosome (very difficult to do) or remove/inactivate the Y (giving rise to an XO female). That in itself would introduce problems in the female.

Turner Syndrome XO Syndrome

| improve this answer | |
$\endgroup$
  • 2
    $\begingroup$ The question asks whether a man "...contains all the genes..." to make a woman, while this answer is mostly dealing with chromosomal makeup and the issue of producing haploid gametes. From a strict/narrow gene perspective, I think the answer to this question is yes. $\endgroup$ – fileunderwater Jan 16 '15 at 8:49
  • 3
    $\begingroup$ It is possible to make haploid stem cells by injecting a sperm in an enucleated oocyte or artificially activating the oocyte without fertilization. See here $\endgroup$ – WYSIWYG Jan 16 '15 at 8:55
  • 1
    $\begingroup$ @WYSIWYG - that is wild; I never knew that! I did know there are some nearly-haploid cell cultures, but I did not know the manipulation of genetic material in oocytes was this far along. $\endgroup$ – anongoodnurse Jan 16 '15 at 9:00
  • 3
    $\begingroup$ @anongoodnurse It was one kickass paper. I was so thrilled while reading it. $\endgroup$ – WYSIWYG Jan 16 '15 at 9:01
  • 1
    $\begingroup$ @fileunderwater - true enough. I guess the answer would be (for me) even if he could get two gametes with X chromasomes, as a male, how will he introduce the genetic material into a manipulated oocyte? The clone seems maybe better. Some of this is new to me. $\endgroup$ – anongoodnurse Jan 16 '15 at 11:16
5
$\begingroup$

Theoretically this should be possible as men carry both sex chromosomes. You would have to find a way to make haploid cells and then have them form a diploid cell with two X chromosomes. Your population would go through a genetic bottleneck which would soon cause a lot of other genetic problems as there is not enough variety.

But besides this rather theoretical approach, there is a real problem with this kind of reproduction: it won't work because of genetic imprinting. This takes place in the egg and as well in the sperm cell and consists of small modifications added to the DNA. This silences this gene and allows the expression of genes specifically either from the mother's or the father's copy of the chromosome.

An example for this would be the loss of a part of chromosome 15. Depending on which copy is lost, this either causes the Prader-Willi Syndome (inherited from the father) or the Angelman Syndrome (inherited from the mother). This article goes deeper into imprinting.

Due to the missing maternal imprinting, the cells constructed from the father will not be viable since the expression of some genes (which would come from the mother) is missing. Nevertheless it has been shown in mice that it is possible to overcome this problem. The researchers deleted the maternal imprinting on one copy of the chromosomes they used, mimicked the fathers imprinting and where able to breed viable off-springs from two female mice without a father. But this approach is rather technical and also error prone since you have to know the imprinting of the mother. The article can be found here.

| improve this answer | |
$\endgroup$

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.