Back when I was a wee lad, I learned most of what I know about the biology of sex from a NOVA special. Even at my young age, I remember seeing the mutant two “headed” spem and those with two tails and even some odd Siamese twin style sperm which were two sperm sort of half connected at the “head”. So, anyway, they always said at the time that these little guys weren’t going to be hitting the egg because they couldn’t swim as fast. But, what would happen if one did? Twins? Some sort of oddness? Has anyone tested this? (On animals through artifical insemination, I doubt anyone’s offering up eggs and sperm to see if they can use mutant sperm).
Wow… my first sex question. I feel so dirty.
“I guess it is possible for one person to make a difference, although most of the time they probably shouldn’t.”
No answer here, but i have seen some of those ‘mutants’ too and pre nova at that. But I can’t recall seeing any mutant eggs. Gotta be some tit for tat and all. Did I just miss them?
You should feel dirty ,Jophiel, the very idea asking such a thing in a place like this.
When the tip of the head of a little spermy breaks through the outer layer of the egg, something changes and the egg will not allow any other sperms to break through (like my scientific language?). If it was a two-headed sperm, only one head would break through. I believe it’s impossible for two sperm heads to fertilize the same egg. I’d be more worried about the integrity of the genetic information contained in a mutant sperm. If it’s screwed up enough to have two heads/tails, then who knows what happened to the info inside.
I have to agree with DD, he’s right about the block to polyspermy (there’s an immediate temporary block and a slower more permananent block to be exact.) The genetic material from the head that made initial contact would be the type to enter the egg. The other head wouldn’t be able to deposit its DNA.
I’d imagine that it’s possible for a 2-headed sperm to have normal genetic information. The DNA located in the sperm head isn’t responsible for the formation and division of the sperm, so it may be OK.
I beg to differ on the impossibility of two sperm fertilization. True in general biology we learn that only one sperm can enter the egg. While it is a rare occurance, two sperm cells can enter the same egg at the same time. And, I imagine, a two headed sperm may have both heads enter simultaneously, before the egg has time to change. To answer the original question, if two sperms (with their appropriate set of chromosomes) entered the egg, a condition called triploidy would occur. Triploidy is where there are three sets of chromosomes instead of the required two sets. The result for some plants and some lower animals is not too bad and may result in viable offspring (maybe even a separate species–depending on one’s definition). For higher animals, however it is deadly and the fetus is spontaneously aborted.
True, natural polyspermy does occur. So, Jo, if you were wondering what a double-fertilization event leads too, bill’s got your answer.
But if you’re wondering what would happen when two-headed sperm meets egg, I don’t necessarily thing polyspermy would ensue. In fact, it might be more unlikely that a two headed sperm would fertilize the egg with each head than would two independent sperm. The fusion of one head might put the other head in a position that would make it difficult to make contact with the egg. It’s not like a two-headed arrow flying towards a target. It’s not automatic polyspermy should a two-headed sperm find the egg.
Mutant eggs also occur – or, more accurately, mutant proto-eggs. During meiosis, only one haploid proto-egg cell out of every eight becomes an actual ovum. Also, even among the ova, only the select few are ripened and burst from the follicle, while the ovoid hoi polloi are reobsorbed by the body. I believe it is now thought that this selection process is not random, but rather works as a quality-checking mechanism.
A book came out not long ago, I think it was called “Sex Wars”, that postulated that these mutant sperms actually serve a function, like doing battle with the sperm from other men if present.
I didn’t read the book, but it may have insight about what happens if a warrior sperm (or whatever) makes it to the egg.