Why is it not possible to fertilise other animals' eggs with human sperm?

Question

Say I was trying to create an Island of Dr Moreau living nightmare by mating humans with animals.

Why would it not be possible to create a zebra/human hybrid by fertilising a zebra egg with human sperm and why can other animals cross-breed with a zebra when humans cannot?

Just to elaborate: I've been experimenting in my basement for the last six months and the best I've done so far is to create a chicken with a human head, but it didn't live very long. Is it worth continuing?

Answer 1

Just to elaborate on another answerer, it is about chromosomal homology. She said that it was because the DNA needed to be nearly identical, and she is correct.

Each gamete has a certain number of chromosomes. Each of these chromosomes must be able to pair up with a chromosomal homolog during the union of sperm and egg (each of these is a gamete). A chromosomal homolog is a chromosome that has a nearly identical genetic makeup as another chromosome. Individual genes may have slight variations or may be defunct, but they are still nearly identical and do not keep two homologs from pairing.

Remember that animal cells are diploid (there are two copies of each chromosome in the cell). Only having one chromosome in each cell exposes the cell to lethal recessive alleles. What this means is that if you have only one chromosome and it has an disrupted gene on it that is essential for cell survivial AND there isn't a backup copy of the gene on another chromosome, then the cell dies. Also, there are many genes that are needed in pairs in order to produce the proper amount of gene product. Lack of one of the genes leads to birth defects (like Cri du Chat syndrome) and other genetic disorders.

This is basically why you can't mate humans and other animals together. The best you could hope for would be a twisted still birth.

This is also why human-alien hybrids in SciFi movies is patently absurd. Aliens wouldn't even have the most distant common anscestor with humans. It would make more sense mating humans with bacteria than with an alien, because we'd have more in common genetically than with the alien.

For more specifics on embyonic development you might check out some books on it at the library. Basic genetic textbooks would help, too. Enjoy!

Good question, by the way.

Answer 2

Simply because the human genome is arranged differently from another species genome. When the DNA in the chromosomes line up during fertilisation the process would stop there because each strand of code would not correspond to each other. Thus a spontaneous abortion would occur. If the process did continue, there would be a waste of resources growing the being as it would die fairly quickly.
It's a bit like sticking a playstation 2 disc into an x box. The x box wouldn't be able to read the code, so it can't run the program.

Answer 3

If you want to create new species, forget about messing about with chromosome numbers - what really counts is genes.

GM crops contain genes from other organisms, and there's no reason that this couldn't be done with humans, aside from the veggie-ethics brigade....transgenic humans are the way to go man.....

Answer 4

Well I bought the zebra dinner took her to the movies and even got her drunk but she wouldn't let me go all the way. Its been 6 month's now should i give up and move onto that cute camel I have seen at the other zoo?

Answer 5

Number of genes in a Chromosome. They are different. A human has 23 genes in one. Other animals have different numbers. Even a homo sepian can't fertilize a homo-erectus.!!

Answer 6

I must tell you the truth, that is how you were born. Your father used his sperm to fertilize a plant in a flower pot & raised a Blooming idiot.
I swear you fell out of a stupid tree and hit every branch on the way down.

Answer 7

try to combine 2eggs and 2 sperms into one cell instead of combining 1 egg and one sperm.. and see the results. this is the 'only' possible way to make the newly formed cell capable of dividing into multicellular being. or so i thought XD

Answer 8

egg and sperm need to have almost identical dna to combine. so only same species can mate successfully. very close genes can combine, like horse and donkey makes a mule. but that is very similar dna.

Answer 9

As far as I know, it should be possible. I think its more of a moral issue. Making new breads, would they be equal, more discrimination as with Civil Rights.

Added:

Ok, the chromosome answers make sence. I forgot about that factor.

Answer 10

No, because the genes are incompatible. You'd have to splice their DNA to make animal/human hybrids.