Question

is O a recessive blood type for all blood types always? (except O blood type of course)

Answer 1

In relation to the A and B blood types, yes. In general, an allele is not intrinsically "dominant" or "recessive" - these are instead relative terms used when considering other specific alleles. A and B alleles lead to expression of A and B antigens respectively on the surface of red blood cells. O alleles do not produce any antigens on red blood cells.

Therefore, if you have both A and O (for example) being expressed at the same time, you will observe A antigens on your red blood cells and the blood type will be considered A as well. Because the A antigen is expressed, it masks the fact that the O allele is present, so A is dominant relative to O and O is recessive relative to A. Replace A with B and you get the same thing.

Side point: If you have both A and B alleles, your blood type is AB and the two alleles are considered codominant. The is because red blood cells will express both A and B antigens equally - one does not mask the other.

Answer 2

wow well said :) i'll take note of that thanks

Answer 3

i guess one cannot say if he's adopted or not by just judging from blood types =))

Answer 4

Actually, you could. Do you have a specific example?

Answer 5

afraid not. im only asking out of curiosity

Answer 6

Alright well for example if the child is type B blood but both parents are type A, the child must have been adopted (or is the son of another father) as neither parent possesses a B allele to pass on.

Answer 7

oh i see...makes sense

Answer 8

so is this also somehow the reason why they say AB is rare?

Answer 9

Well AB is rare because A and B alleles are less common in general than O, so the chance of a parent with A and a parent with B producing a child is less common than say two parents of type O. Even a type A and B parent do produce a child, there is no guarantee that the child receives an A and B allele (since parental genotypes may be AO and BO rather than homozygous).

Answer 10

i see...that makes a lot of sense..biology is indeed intriguing