Blood types

[Mark154]

What's the the difference between positive and negative blood types?

[fo3nix]

http://www.blood.co.uk/pages/e13basic.html

covers the basics :)

[Mark154]

All is now clear.

Thanks fo3nix

[MargeB]

We're all human. Why should different antigen systems develop?

[stevie21]

Diversity provides advantages in the gene pool.

[MargeB]

Thanks stevie, that makes it clearer. So the genes became more diverse in order to have advantages? Is that how we got different blood types?

[stevie21]

Diversities in the gene pool susrvived because they provided advantages. They initially arose as random mutations but survived as they made the organism fit their environment somehow better : you make it sound like a conscious choice to change to *seek* an advantage. We get genetic mutations in every generation, it's normal. Natural selection and all that niceness.

The blood groups are A, B, AB and O.
Those with O are more susceptible to cholera, AB is the most resistant. As you inherit 2 chromosomes (one from each parent) blood type A means you have AA. B = BB. (remember AB is better in terms of cholera than either here).
If 2 AB parents have kids, only half their kids are likely to be AB, some will be AA, some BB, so we never get to the stage where only one blood type dominates (the other blood types all have their own advantages too : O is more resistant to malaria).

Make more sense?