If two sperm fertilize one egg which is a very rare occurrence in 1% of the case the embryo can't survive. So, two sperm cannot fertilize the same egg.
Combining two sperm wouldn't work. There just isn't enough in a sperm to sustain an embryo early on. What about removing the DNA from an egg, and adding two sperm to that? Theoretically you'd end up with a child with the DNA of both dads, and just a bit of the donor's DNA.
Occasionally, two sperm are known to fertilize a single egg; this 'double fertilization' is thought to happen in about 1% of human conceptions. An embryo created this way doesn't usually survive, but a few cases are known to have made it — these children are chimaeras of cells with X and Y chromosomes.
For sperm, some scientists say, love and war are one and the same. According to the so-called kamikaze sperm hypothesis, sperm from different men hanging out in the same vagina may sabotage each other in the run for the egg. New findings, however, cast doubt on this idea.
Sperm cells are incredibly complex. Just like Humpty Dumpty, it would be almost impossible to take them apart and put them back together again.
The biological phenomenon of giving birth to twins with two different biological fathers is called heteropaternal superfecundation. In a rare and surprising event, a 19-year-old Brazilian woman gave birth to twins who belong to two different biological fathers.
Usually, two sperm cannot fertilize the same egg. The reason behind this is that when one sperm comes in contact with zona pellucida then some changes occur in the membrane which prevents the further entry of sperms which is called polyspermy.
Each sperm cell contains half the father's DNA. But it's not identical from sperm to sperm because each man is a mixture of the genetic material from his parents, and each time a slightly different assortment of that full DNA set gets divided to go into a sperm.
There is ample evidence to show that as millions of human sperm cells swim towards a waiting ovum or egg, only one gets to fertilize it. Now, a new study shows that even though the fastest and most capable sperms reach the ovum first, it is the egg that has the final say on which sperm fertilizes it.
Like your genome, each gamete is unique, which explains why siblings from the same parents do not look the same. Following fusion of the egg and sperm, another type of cell division called mitosis occurs, producing two identical cells from one.
Egg donation and surrogacy allow two gay men to have children genetically related to one partner and the egg donor, but not to both. It's the same dynamic for lesbians and sperm donors.
Researchers from Stockholm University and the Manchester University NHS Foundation Trust found that the egg effectively chooses the sperm it wants, and rejects the others. "Human eggs release chemicals called chemoattractants that attract sperm to unfertilised eggs.
The preliminary findings indicated that X spermatozoa are larger and stronger than Y spermatozoa, suggesting that they are more stable in an acidic pH than Y spermatozoa (Landrum and Shettles, 1960; Shettles, 1960).
The results showed that there were significant differences in several parameters of semen quality between first and second ejaculations. No significant differences were also found on Ca and Mg concentrations and Ca/Mg ratio. The TAC level was significantly higher in the first ejaculation than the second one.
To form identical or monozygotic twins, one fertilised egg (ovum) splits and develops into two babies with exactly the same genetic information. To form fraternal or dizygotic twins, two eggs (ova) are fertilised by two sperm and produce two genetically unique children.
The quick answer to this question is that, in a twin pregnancy, it is the mother's genes that determine twins. First up, giving birth to identical twins is not genetic, but conceiving fraternal twins is. The mother may have the genetic trait of releasing two eggs in one menstrual cycle.
Multiple pregnancy usually happens when more than one egg is fertilized. It also can happen when one egg is fertilized and then splits into 2 or more embryos that grow into 2 or more babies. When one fertilized egg splits into 2, the babies are called identical twins.
Fertility treatment
Some fertility drugs work by stimulating a woman's ovaries, which can sometimes cause them to release more than one egg. If sperm fertilizes both of these eggs, this can result in twins. In vitro fertilization (IVF) can also increase the chance of conceiving twins.
If twins are a boy and a girl, clearly they are fraternal twins, as they do not have the same DNA. A boy has XY chromosomes and a girl has XX chromosomes.
In 99.9% of cases boy/girl twins are non-identical. However, in some extremely rare cases resulting from a genetic mutation, identical twins from an egg and sperm which began as male (XY) can develop into a male / female pair.
Yes, it is possible for a baby to have two biological fathers through the phenomenon known as “bipaternalism” or “heteropaternal superfecundation”. This occurs when a woman ovulates twice within the same menstrual cycle and has sexual intercourse with two different men during that time.
This means the baby has three genetic parents: the father who supplied the sperm, the mother who supplied both womb and the egg nucleus, and an anonymous donor who supplied healthy mitochondria. Of these, the mitochondrial DNA is by far the smallest contribution.
Chimerism is a rare congenital condition involving one person having two different sets of DNA. There are a few instances when it can occur: when a fetus absorbs a vanishing twin during pregnancy, when fraternal twins trade chromosomes with each other in utero, or when someone has a bone marrow transplant.
Whereas sperm quality is at the best levels between ages 30-35, motility is best before age 25. And as with semen quality, motility declines dramatically after age 55.
Y sperm: are faster but survive for less time in the female genital tract. X sperm: are slower, but they are more resistant and therefore survive longer.