Is it possible fertilization of one egg by two sperm cells

[Pawelk198604]

I recently watched a science program about fertilization, it was mentioned that only one out of millions of sperm fertilizes the egg.

I wonder if it is possible that the egg got not one but two sperm cells.

[ZedNova]

Yes i think so. Although i don't know the effects it has on the embryo.

[Kryten]

It depends on how you define 'sperm' and 'egg'; it's certainly not going to result in viable offspring in a mammal, and probably not any animal, but pretty much anything goes in plants.

Edited June 9, 2014 by Kryten

[phoenix_ca]

http://en.wikipedia.org/wiki/Polyspermy

[softweir]

Apparently not. The ovum is very well evolved to prevent this. *IF* it did happen, then having 3 copies of every chromosome would either cause the embryo to self-abort immediately, or would lead to rampant, massive failure to develop properly and a very quick death, long before the pregnancy was detectable. There are several conditions where a chromosome is doubled up so instead of a pair, there are three, and they generally have serious effects on the individual.

Something sort of similar to double-sperm-fertilisation has been observed in IVF labs and in nature where the unfertilised ovum managed to divide before fertilisation, creating two "clone" ova, each of which was then fertilised by a sperm. The two cell lines may separate and develop two individuals - twins - or the cells may mix together and create a single, hybrid individual. When the two cell lines have contradictory gender chromosomes (ie, one is XX and one XY) then the foetus has a very significant chance of going on to develop ambiguous genitalia - a hermaphrodite.

[sgt_flyer]

It seems that such cases occurs, but the embryo is generally not viable. (One of the only documented cases (in 2007) where the embryos survived had seen the egg split to create twins. Although those twins are stated as 'chimeras' where some of the organs of one can end up in the other body.

[K^2]

Although those twins are stated as 'chimeras' where some of the organs of one can end up in the other body.

Division in chimeras isn't at organ level. All it really means is that zygote was made up of cells with different genetic makeup at some point. It's quite common in some animals. Very rare in humans. You can end up with entire organs or particular tissues having different genotype than the rest of the organism, of course. But you can also end up with cells fairly thoroughly mixed. Something similar happens to mammal females, where only one of the two X chromosomes is actually necessary. The other one goes dormant, making up the Barr body in the nucleus. Selection of which X chromosome goes dormant happens early on at random and persists through further divisions. As a result, mammal females are chimera-like on any X-linked gene. A great example of that are calico cats. The color of their fur, black or brown, is set on the X chromosome. So a female with two different color genes on two different X chromosomes ends up having patches of black and brown fur. This reflects the fact that it's not different organs, bur rather different areas of the cat's skin that has differences in genetic expression. Chimera cats have similar fur patterns sometimes, but can be of either gender, naturally.

[Pawelk198604]

It seems that such cases occurs, but the embryo is generally not viable. (One of the only documented cases (in 2007) where the embryos survived had seen the egg split to create twins. Although those twins are stated as 'chimeras' where some of the organs of one can end up in the other body.

This is really scary, like some cheap Class B horror , could you give a link to this article?

[nnw890]

When 2 sperm fertilise 1 egg it is called diandric triploidy. It causes the embryo to have 2 sets of paternal chromosomes instead of 1 and therefor 69 chromosomes rather than 46.

In my case, I had a 12 week scan. Baby had all organs, healthy heartbeat, arms and legs and was moving around. The only alarm bells were increased fluid behind the neck, measuring a few days smaller than expected and the placenta not looking quite right. It took a blood test and a biopsy of DNA from the placenta to confirm triploidy. 

Often the baby will miscarry or will be a stillbirth. Occasionally, babies live a few hours or days after birth and look relatively normal but very small. One baby lived to 10 months old.

Yes it’s like something from a horror movie but not in the way that you think. It happens in 1-2% of pregnancies. 

Heres a link so you can all educate yourselves:

 

 

[sevenperforce]

Note that in all fertilizations, the ovum is penetrated by many, many separate sperm, but only one reaches the nucleus to fuse.

[Snark]

Also, please note that this thread is an ancient one, years old, before it just now got revived.  So if you're thinking of responding to a post in this thread, it's worth checking "how old is the post I'm responding to?" and considering whether it actually needs a response at this point. 

[nnw890]

Sevenperforce, as I said, in most cases of triploidy, 2 sperm fertilise the egg and fuse with the nucleus, meaning that the fetus has 3 sets of chromosomes instead of 2. 2 paternal sets (from each of the sperm) and 1 maternal set. A chemical reaction in the egg should only allow one sperm and close off to all others, but occasionally this does not happen. It is this malfunction that causes the fetus to be incompatible with life, though in some cases it can survive until shortly after birth 

 

 

 

 

[KerikBalm]

trisomy is really really bad.

Of the 23 pairs of chromosomes, only 1 pair can become a triplet and still have the baby survive until birth, and only specific pairs:

https://en.wikipedia.org/wiki/Trisomy#Human_trisomy

Chomosome pairs 8,9,13,21,22,23 (sex chromosomes), can "tolerate" trisomy. That means 17 out of 23 chromosomes cannot come as a triplet instead of a pair.

2 sperm can fuse with an egg in rare cases, but thats going to introduce a 3rd copy for 17 out of the 23 chromosomes that cannot tolerate a 3rd copy... the egg will not be viable.

Chromosome 21 is the smallest, or just about the smallest chromosome, and its the most common form of trisomy in humans, because the other forms of trisomy are lethal and you won't find humans that survive other forms of trisomy. Thus the most familiar case of trisomy that you may be familiar with is Down Syndrome... and thats just chromosome # 21, the smallest chromosome, with a 3rd copy.

Many of the other forms of humans with trisomy are mostly observed when there is an additional partial copy of a chromosome. In some cases that full chromosome is lethal, but sometimes a smaller fragment of the chromosome is not embryonic lethal

[nnw890]

Yes that’s all true. Triploidy is where ALL 23 chromosomes are tripled because 2 sperm have fertilised one egg or egg has duplicated chromosomes before fertilisation. That’s what happened in my pregnancy. Baby doesn’t look like an alien. Looked surprisingly normal on 12 week scan. All organs there, heart beating healthily, head looked normal, arms, legs, fingers, toes. But as you say it’s not compatible with life. Triploidy babies have lived a few hours after birth at best. 

[magnemoe]

On 10.6.2014 at 1:35 AM, Pawelk198604 said:

This is really scary, like some cheap Class B horror , could you give a link to this article?

Nothing so dramatic, its just that you get two set of dna, if fathers has different races you can get patches with different skin color. 
chimeras tend to be two zygotes, with say 8-24 cells melt together, and they have different father. 
Rare as female has to get pregnant with two males with not much pause between, you will also hardly notice unless fathers had different skin colors. 

Was an lady who took an dna test who was compared with her child for some reason and they found she was not the mother, but child was related to her. 
They did some more testing as father matched so not switched babies, found that lady was an chimera and the place they took genes from had the other genes. 

[Exoscientist]

 

 I hadn't heard of trisomy. But I heard of cases where fraternal twins actually had different fathers. In this case separate eggs were fertilized by different sperm during the same pregnancy. 

https://en.wikipedia.org/wiki/Superfecundation

 

  Bob Clark

[nnw890]

You are talking about two eggs being fertilised by sperm from different fathers.

This is not the same as 2 sperm fertilising one egg, which causes triploidy and is incompatible with life

[YNM]

Despite being a "great 'ol dig", it's an interesting thread in any case.