blood groups/dna

[jannyneve]

if brothers have different blood groups how similar would their dna be?in a recent court case it was said by an expert witness that the odds were 6000 to 1 of them being a close match to each other,but what are the odds if the blood group is different?also what about half brothers,how close a match would they be to each other?thanks very much.

[bobjim1705]

EDDIE51, it is entirely possible for brothers to have different blood groups.

When sex cells are produced (egg/sperm) the chromosomes arrange in what is known as "independent assortment." Basically, before a cell divides, they line up along the middle of the cell, and can line up any way they please.

When the resultant sex cells are formed, each will have a different chromosome (or indeed, a different PART of a chromosome) in it, and each chromosome will contain different genetic material.

Ultimately, this means that brothers could be very similar, or they could be a world apart. The chance of them being identical is very very very low.

With half brothers, they would share some of the same maternal/paternal DNA, but would have different DNA from the other parent.

[LazyGun]

It is entirely possible for brothers to have different blood groups and have the same mother/father.Their DNA however would show familial similarities.
No idea if the odds you quote in your question are correct, but they would not change if the brothers had different blood groups.
As half brothers, the odds would be longer, but their would still be DNA similarities.

As an example: Father group A Mother group A.
Possible blood groups for any children ; ABO Group A or O.

Father Group O Mother group O.
Possible blood groups for any children ABO Group O.

Father Group B Mother Group B
Possible blood groups for any children B,O

Father Group AB Mother Group AB
Possible blood groups for any children, A,B,AB

and so on and so on.