Talk:Parthenogenesis

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The mouse that was created by Japanese scientists was the result of *combining* two eggs. That is completely different to development of an organism from a single egg. The entire Parthenogenesis section talks about a *single* egg.

It seems to me that if Parthenogenesis is defined as "growth and development of an embryo or seed without fertilization by a male" then the Parthenogenesis section needs two subheadings: one for development from a single egg, and another for development from two eggs.

---

My genetics course said that parthenogenesis in mammals is impossible, or at least extremely difficult. Obviously, there are examples of experiments on this main page, but I suspect they had problems with this: parthenogenesis is difficult for mammals because mammals posses a unique genetic characteristic: X-linked innactivation. The general idea is that mammals, more so than other vertebrates, are likely to have a female inseminated by more than one male at a time, and to actually have embryos within the same womb from different fathers. This led to the natural selection directed process whereby certain genes from the male chromosomes are methylated, turning them off, etc. and this tends to give that male's embryo's an advantage over the others. Meanwhile, the other embryos are doing the same thing; this leads to a tug of war, essentially, while at the same time the mother's genes in the embryo are methylated in a way that will favor the survival off all of the embryos. --->At any rate, the practical result is that if two DNA strands from only the mother were to combine (the parthenogenesis process as it normally occurs in certain lizards), the resulting mammal embryos would lack essential X-linked inactivations. X-linked innactivation mistakes, when they occur naturally in humans because of non-disjunction, etc., cause crippling genetic disorders in humans, i.e. "Laughing Puppet Syndrome" and others. I would imagine that any live parthenogenesis mammal births would suffer from devastating genetic syndromes. More research for the wiki article needs to go into that---Ricimer, April 12, 2005

I too was told by my Biology Professor that Parthenogenesis was possible in mammals, albeit very rare. He even told us that it was possible in humans and had been documented. He told us of women who were freaked out that their daughters looked just like them, and other women who went religious because of their pregnancy. This is coming from my biology professor and I'm not sure if he was telling the truth or not. He seemed to specialize in studying swamp life more than basic genetics. SargeAbernathy 02:29, 25 April 2006 (UTC)


Unless someone has a source to back up the claim that snakes can reproduce by parthenogenesis, it should be removed (as I have done) and stay removed.

Parthenogenesis is well noted in some species of lizards and salamanders (such as the Jefferson's Salamander and various Blue Salamander hybrids) for which there are no males. I'm unaware of anything remotely like that in snakes, unless you want to count false pregnancies (where a female snake which has not been impregnated lay unfertilized eggs, or in the case of ovoviviporous [spelled wrong, trust me] snakes, weird jelly-bean-like nuggets).

I know enough about reptiles and amphibians that I'm comfortable making those edits, but I'm not so sure about Turkeys... Anyone have some evidence they wanna post?


-- I've just done some research and parthenogenesis has occured in some snakes, but it is by no means a common occurence (as it is with whiptails and some salamanders) and is not very well understood. As far as I could find are four known occurences (one timber rattlesnake which produced one litter, one wandering garter snake which consistently produces litters for ten years, a brahminy blind snake, and one other snake).

Contents

[edit] Sharks

It would be nice to have some information about Sharks on this page. Here's a general article on putative parthenogenesis in Sharks. --Viriditas 10:13, 7 Sep 2004 (UTC)


The exact process, difference in parts involved and biochemistry, etc, still needs expansion and explanation. --Tchalvak

Parthenogenesis in snakes is noted in quite a few live-bearing species. Most notable are the rat snakes, with a particularly interesting article recently (2-3 mos ago) regarding a scaleless rat snake that reproduced via parthenogenesis. Will ref article once I relocate it. Other snakes with records of parthenogenic births are listed in "Snakes of the Southeast" by Chad Minter.

As for turkeys, and other birds, parthenogenesis has been noted. The following is a link to a research paper on the chemistry affecting parthenogenesis in unfertilized Turkey eggs. It is worth noting that while many birds occasionally have parthenogenic hatchings, Turkeys are considered to be the most likely to have such hatchings.

http://oregonstate.edu/Dept/animal-sciences/poultry/

Within the mammals, no natural parthenogenesis can occur.

[edit] Fictional mammalian parthenogenesis

  1. In the future, please sign your comments.
  2. Please read WP:VAND, Anakin Skywalker is alleged to be born without a father according to the Darth Vader article.

I would appreciate an apology for your comment on my talk page. Karmafist 04:48, 10 November 2005 (UTC)

Sorry I forgot to sign. But please leave the silly nonsense out of a scientific article. I have no idea what the ficitional backstory is for Darth Vader, but no one interested in biology cares about some fictional fantasy (which probably isn't parthenogenesis anyway). I did think there was some mention of the father in the very forgetable "episode one", but maybe I remember wrong.
And no... don't add Jesus, Saint Anne, Golem, or whatever other myth/fiction either. Lulu of the Lotus-Eaters 04:56, 10 November 2005 (UTC)
Hmmm... more things that don't belong in this article. From Virgin birth:
Dolly the sheep is probably superfluous too, but a moderately plausible case for a link could be made. Lulu of the Lotus-Eaters 05:28, 10 November 2005 (UTC)
Parthenogenesis is an extremely important element of mythology world-wide. Until such time as someone has written a separate article on it, I think it's entirely appropriate for this article to have a section on "Parthenogenesis in mythology and popular culture". Angr (t • c) 22:01, 15 May 2006 (UTC)

[edit] Parthenogenesis in Humans

Reference links to the study of Virgin Births in Humanity:

http://ourworld.compuserve.com/homepages/dp5/sex2.htm http://www.all.org/abac/aq0202.htm

It seems that the idea is of it being a natural oddity has been passed around, but never any clear documented case. SargeAbernathy 02:36, 25 April 2006 (UTC)

No offence, but that shouldn't be included because there is no data for it. Looking it up, no cases for "virgin birth" in humans have been declared actual since genetic testing has been available (which can easily test for it). Sad mouse 04:13, 21 December 2006 (UTC)
A geneticist I heard talking about human parthenogenesis mentioned a number like one out of a million births, which would mean a couple of hundred living individuals in the US and just a handful of new cases a year. If we assume that number to be correct, it would be very difficult to identify any real cases. Some births would be to couples who would not notice anything strange. Some women would not be taken seriously when they said they had had no sex, and no one would investigate.
Even if there is no data for it, it could be included with the lack of evidence mentioned. Something like: "There have been alleged cases of human parthenogenesis. However, none of them has been confirmed."
But it would be good if we first could get a feeling for what people in the scientific community believe. How many are convinced it never happens? How many are convinced it happens? And how many admit that no one knows? Mlewan 19:42, 18 January 2007 (UTC)

[edit] picture

Let me quote from the article about Kaguya, the mouse pictured in this article:

This is not a cloned animal because cells from two individuals are used. This cannot be called asexual reproduction, or parthenogenesis, for the same reason.

Why is this picture in the article for parthenogenesis, if it is not an example of parthenogenesis? I see someone else mentioned this above, but that post was not signed. I think that a different picture, one that actually represents the topic at hand, would be more appropriate. romarin[talk to her ] 15:06, 9 June 2006 (UTC)

I agree. Yank the picture. Having a picture of something that is specifically not parthenogenesis and says it's not parthenogenesis on the page for parthenogenesis is a bit like having a picture of a turkey on the page for a chicken and saying 'This is a turkey, not a chicken.'

However, if an image is really wanted here, speaking of, how about a turkey? As far as I know they are the only known warm-blooded animal known to undergo the process. 69.181.120.218 09:08, 16 August 2006 (UTC)

[edit] Genetic variation

Unless I am missing something central, the second paragraph

Parthenogenesis has nothing to do with artificial animal cloning, a process where the new organism is identical to the cell donor. Cloning does not require eggs. Parthenogenesis is truly a reproductive process which creates a new individual or individuals from the naturally varied genetic material contained in the eggs of the mother. A litter of animals resulting from parthenogenesis may contain all unique siblings without any twins or multiple numbers from the same genetic material, but they would all be female.

must be incorrect. Isn't it obvious that the genome of an embryo produced by a the mother without involvement of any other individual must be identical to the mother's own genome? Where would any other genes come from?

No, they are not identical. Consider that the mother will have two alleles for many different genes. In making an egg, only one allele goes into the egg, and that one allele gets duplicated, meaning the offspring has only one allele for that gene. So while the offspring has only DNA from the mother, it does not have all the DNA from the mother and is therefore not identical. Sad mouse 04:11, 21 December 2006 (UTC)

A second part of the same edit (on Aug 4 by 63.232.2.106):

Parthenogenetic populations must be all-female because there is no contribution from a male. The offspring may be capable of sexual reproduction, however, if that exists in the species.

also seems logically impossible. If the population must be all-female, how would there be any males to reproduce sexually with? Mglg 20:48, 16 August 2006 (UTC)

That is a typo, I'll go and fix it. Sad mouse 04:11, 21 December 2006 (UTC)


I think I know how this happens, but it's not obvious. In sexual reproduction, the body produces the gametes (sexual reproductive cells, i.e. ovum and spermatozoon) by meiosis, where the cells produced have exactly half the genes than a normal cell. A normal cell has always two copies of every gen, and one copy of this gen is chosen at random at the time of the meiosis. In this way, gametes have all genes, but a random copy of every gene. This is called recombination, and is one of the reasons siblings are not identical amongst themselves in sexual reproduction.

An example: say the father has to sets of genes, A and B, and the mother also two sets, C and D. So the possibilities in generating a spermatozoon are choosing a gene from pool A or one from pool B. In the mother it's the same, a gene from pool C or from pool D can be chosen. So the sons and daughters can have any of all the combinations of genes: AC, AD, BC or BD.

So let's examine parthenogenesis. The mechanism of parthenogenesis is not explained in the article (and I am not a biologist myself), but let's say the gametes are generated in the same way by the mother, an ovum and a spermatozoon. They each have half the genes of a normal cell, and a random copy of every gen. But in this case, both gametes are generated by the same body, and therefore have a random copy of the same pool of genes. So if the sets of genes are in this case A or B, and both spermatozoon and ovum have to "choose" from the same pool, the combinations are AA, AB, BA or BB (AB and BA are really the same, the order is not important).

So the daughter, born by parthenogenesis, has a random recombination of the same genes as the mother, but they are not identical.

The advantage of sexual reproduction can be seen here: genes propagate much faster, and the variability of a population is much higher.

La Vida es un Carnaval 09:26, 3 September 2006 (UTC)

[edit] Citing sources with ref tags

I would like to rearrange the citations here using <ref> tags, so that it will be easier for me to add inline citations. Anybody have an objection to this? --Zvika 19:38, 9 October 2006 (UTC)

Go for it, although it makes the hard-to-read typeqriter font in the edit window even harder to read, and the name=xxx function has to be the first appearance of the ref, making it hard to move text around. There was a proposal to allow all the references to be in a reference section at the end, then use all short-form cites anywhere in the article, which would be ideal. Edison 15:10, 21 December 2006 (UTC)

[edit] Komodo's Parthenogensis

http://www.cnn.com/2006/WORLD/europe/12/20/uk.komodo.reut/index.html

According to this article they give birth to all males and nothing of that sort is mentioned in this article at all... I don't have a biology background and think someone else would be better suited to edit this article. But is this the first time parthenogensis has been known to produce all males or is something wrong here? Sepharo 20:37, 20 December 2006 (UTC)

Unfortunately, whoever added the information that "Recently, the Komodo dragon which normally reproduces sexually was found to also be able to reproduce asexually by parthenogenesis" is mistaken. The CNN article DOES NOT say that *the* Komodo Dragon has been found to reproduce through parthenogenesis. It says that *A* Komodo Dragon was found to be able to reproduce that way. That is a VERY big difference. If you look at http://www.courant.com/news/nationworld/world/wire/sns-ap-virgin-dragon,0,7186513.story?coll=sns-ap-world-headlines&track=email_newsletter you will see what I mean. Anyway, I'm going to leave this up to an expert. Cereal Box Conspiracy 00:39, 21 December 2006 (UTC)
Actually two females, and reading the Nature paper it looks good. Sad mouse 04:08, 21 December 2006 (UTC)
I added a "fact" tag to the info in the article which gives technical details not in the cited reference, about "polar bodies" or some "meiotic" thing being responsible for the fertilization. Please provide a source so it does not have to be removed as original research. There is a paper in Nature and someone with access to it and the scientific knowledge to follow it should include it as a better reference than the CNN or AP reports. [1] explains why the offspring will all be male in the Komodos. Edison 15:06, 21 December 2006 (UTC)
Reading the Nature paper, there is nothing in it about the reproduction not being completely asexual, so I removed that sentence (I did add the reference though). Sad mouse 18:04, 21 December 2006 (UTC)

[edit] Changes to the introduction

Parthenogenetic populations will be all-female if two like chromosomes determine the female sex, but male if the female sex is determined by unlike chromosomes (as in the Komodo dragon), because the process involves duplication of a single sex chromosome. I changed this from "because the process does not involve a male" to "because the process involves duplication of a single sex chromosome. The problem in generating a YZ female is not that a male gamete is required, but because duplication of a single chromosome will give ZZ or YY, but not ZY. Sad mouse 04:07, 21 December 2006 (UTC)

As with all types of asexual reproduction, there are both costs (reduced genetic diversity generated) and benefits (reproduction without the need for a male) associated with parthenogenesis. I added the costs and benefits. Sad mouse 04:07, 21 December 2006 (UTC)

Parthenogenesis is distinct from artificial animal cloning, a process where the new organism is identical to the cell donor. I changed it from "totally different" to "distinct". Sad mouse 04:07, 21 December 2006 (UTC)

I removed the part saying that all offspring would have to be either male or female. That is not true, depending on the genetics of the organism in question. If someone has looked at the sex determination system of every organism that can undergo parthenogenesis and shown that it is incompatible with both males and females being born, I'll stand corrected, but unless someone has, this should not be added. Consider for example a species which uses temperature to determine sex, in that case a single hatchery could give both males and females. Sad mouse 04:07, 21 December 2006 (UTC)

In theory, the process could be used to reproduce humans after extensive testing and perfection. I added "in theory" - we do not know it is possible until it is done. Sad mouse 04:07, 21 December 2006 (UTC)

[edit] Parthenogenesis is sexual reproduction not asexual.

Asexual reproduction produces clones, by mitosis. It is not defined as involving two individuals, otherwise self-fertilization would be considered asexual reproduction. It is not. Sexual reproduction involves haploid gametes, produced by meiosis, like parthenogenesis.


[edit] Evolutionary Aspects of Parthenogenesis

How is it possible that a trait that yields the abiltity to self-fertilize is selected for? To me, a non-bilologist, the most striking omissoin in the article is the lack of information on the evolutionary biology behind parthenogenesis. It also makes the comment

"...The CNN article DOES NOT say that *the* Komodo Dragon has been found to reproduce through parthenogenesis. It says that *A* Komodo Dragon was found to be able to reproduce that way..."

that much more compelling in terms of the evolutionary significance. IMHO. 64.73.41.24 20:37, 25 January 2007 (UTC)


[edit] Hybridogenesis

Could somebody who has an understanding of hybridogenesis clarify this section? I have read and reread the section, but it continues to sound like it is contradicting itself. I very easily am missing something, but even so it could use clarification. Thanks! 70.234.233.35 06:27, 26 January 2007 (UTC)

I tried to clarify it a bit and linked to a site that has a graphical representation (which is a lot easier to understand than the verbal). If someone can draw a graphical version of their own that'd be great, the website I linked copyrights everything so we couldn't use theirs. One Elephant went out to play... 15:36, 13 March 2007 (UTC)

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