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die_kuestenwache t1_j36z7gg wrote

There is a mechanism called genetic imprinting in higher mammals, which is thought to make the genesis of a fully functional organism without both a full set male and female genes highly unlikely to succeed. It is a topic of ongoing research, whether it is still possible to induce parthogenesis in a lab. It has never been observed in mammals in nature.

[Edit] this took me like 5 minutes to google. But I thought it was so interesting that I summarized it as a thank you for making me learn something today.

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Bbrhuft t1_j3giwdm wrote

About 30 years ago, mother in the UK asked for her child to be medically examined because his face was quite asymmetrical, genetic analysis failed to detect any paternal DNA in his blood. After some complex genetic analysis doctors came to the rather startling conclusion that he was a parthenogenetic chimaera, about half his cells only contained DNA from his mother. The child died a few years later, but his death wasn't related to his condition.

They concluded it is was most likely an unfertilised ovum divided parthenogenically (without fertilisation), it almost formed a teratoma (ovarian teratomas form partenogenetically) but one half was fertilized by a sperm. The result merged to form a viable foetus.

The nearest recognised example of a human virgin birth.

Here is the article.

Strain, L., Warner, J.P., Johnston, T., and Bonthron, D.T., 1995. A human parthenogenetic chimaera. Nature genetics, v. 11, no. 2, p. 164–169.

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iayork t1_j373lr0 wrote

There aren’t any natural cases of mammalian parthogenesis, but it’s been done in the lab - with a fair bit of tricky intervention.

> Parthenogenesis, a way of generating offspring solely from unfertilized oocytes, is limited in mammals because of problems arising from genomic imprinting … Parthenogenetic offspring, in which an individual develops from a single unfertilized oocyte, have not been reported in mammals … Here, we report live mammalian offspring derived from single unfertilized oocytes, which was achieved by targeted DNA methylation rewriting of seven imprinting control regions. Oocyte coinjection of catalytically inactive Cas9 (dCas9)-Dnmt3a or dCpf1-Tet1 messenger RNA (mRNA) with single-guide RNAs (sgRNAs) targeting specific regions induced de novo methylation or demethylation, respectively, of the targeted region.

—Viable offspring derived from single unfertilized mammalian oocytes

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everythingiscausal t1_j3852eq wrote

For someone who knows nothing about any of this, how does this differ from cloning?

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CuppaJoe12 t1_j39j3n0 wrote

With cloning you get an exact copy, at least in terms of DNA sequence. This is done by copying a body cell called a "diploid cell," which has a full copy of an individual's DNA.

With parthenogenesis, you do not get an exact copy. You take two haploid gametes, aka sex cells, and implant one into the other similar to how a sperm implants into an egg. The difference is that in this case, it is two egg cells ("oocytes") from a single mother instead of a sperm and an egg from two different parents.

Most genes (with a few exceptions, particularly for male offspring) consist of two copies, one from the father and one from the mother. The grandfather and grandmother of the parthenogenetic offspring.

Whereas the mother has one copy each from the grandmother and grandfather (again, with some exceptions) the parthenogenetic offspring might get two grandmother copies, or two grandfather copies, or it might be the same as the mother with one copy of each. However, with how many genes there are, there is essentially a zero% chance the offspring gets one of each for every gene like the mother has. Thus, its DNA is different from the mother.

This is the same reason you are not a genetic copy of your brothers and sisters. In this case, there are 4 grandparents and 4 possible parings instead of 2 grandparents and 3 pairings for parthenogenesis.

Edit: perhaps an easier way to explain this. If two clones or two identical twins were to mate, their offspring would be genetically identical to parthenogenetic offspring. It is the most extreme form of inbreeding possible, but each offspring would still have unique DNA like brothers and sisters are unique from each other.

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Bbrhuft t1_j3gj0o2 wrote

Here an interesting article about a child that was a parthenogenetic chimaera, about half his cell only had DNA from his mother.

Strain, L., Warner, J.P., Johnston, T., and Bonthron, D.T., 1995. A human parthenogenetic chimaera. Nature genetics, v. 11, no. 2, p. 164–169.

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HaveSomeBean t1_j373mo6 wrote

Depends on how religious you are. (/s)

It is technically possible and has been done in labs and extreme cases. No mammal known actively reproduces asexually in nature.

https://en.m.wikipedia.org/wiki/Parthenogenesis#Mammals

The mammal section outlines some cases where it’s happened in lab setting and further below it outlines the basic mechanism

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DifferentCard2752 t1_j3b39pn wrote

A related note, and scientists correct me if I’m wrong, but if it were to happen, I believe the offspring could only be female. Unless the mother was a reproductively-able hermaphrodite (synchronous) and an internal testis released a sperm cell and it met up with a egg. In that case I have no idea what it’s called but it has allegedly been recorded 11 times. All those offspring were male.

https://pubmed.ncbi.nlm.nih.gov/19155947/

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