REPRODUCTION

[nykkieberry]

Can somebody please explain how one egg and one sperm can make multiple babies?? I know we did this at school but it's a long time ago!

[5029]

It doesn't. It takesone of each for each baby, or else more than one nucleus in each egg

[WaldoMcFroog]

Sorry 5029, but that's not quite right.

A single fertilised egg travels down the fallopian tubes and embeds itself in the soft blood-rich wall of the uterus.

At that point it is a single celled entity. This then splits by binary fission producing two cells. These then split giving 4 etc etc. Identical twins occur when something goes wrong with the fission, i.e. the four cells split completely, giving 2 lots of four cells, rather than one of eight, but from then on split and multiply correctly, thus resulting in to embryos with entirely identical genetic information.

Non identical twins are the result of two fertilisations occuring.

[Waterwolf]

And if the sets of cells don't separate completely, you end up with conjoined (Siamese) twins.

[cutie654321]

dunno