1. What are the odds of having an O+ blood type and having a sister with a AB+ blood type, and having the same parents?

2.

3. This is tricky, I'm just doing this by mendelian genetics
ok well first the ABO group.

There are 6 chromosomal arrangements
OO, OA, OB, AA, BB, AB. (therefore 1/36 that any 2 people are any genotype)

For this to be at all possible the parents would have to be OA & OB,
therefore the probability would be 1/4 per child, then 1/16 for this combination. (Then it would be 1 in 2 for rhesus pre child, 1/4 overall hence total probability would be 1/64)

But if you want to take in the likeliness that each parent would have either of these (ie 41% of population are A (as in OA or AA) and 9% B, but this varies with ethnicity), this gets messy because you also wouldnt know if a parent is AA or OA or indeed OB or BB.

So I suppose I havent actually really answered your question but it's more complicated than I thought when I first started typing!

4. Both of my parents have O+ blood.

I have B+ blood.

5. Originally Posted by leohopkins
Both of my parents have O+ blood.

I have B+ blood.
then they arent your parents, atleast not one of them and im pretty sure its your father by best guess xD
your parents can only give O gene so where the B gene come from in your case must be another guy that isnt your father, or mother

What are the odds of having an O+ blood type and having a sister with a AB+ blood type
your parents can be A and B and have the gene for for O so your sister got the A and B form your parents while you got the Os

6. well ... your parents genotype would be AO and BO ...
So the Mendelian genetics of tit would be 25% for AB and 25% for OO.

But looking at the population as a whole .... that is a very rare combination!!!!

7. That doesnt make sense, AO & BO are the same as OA & OB, the A and B should be expressed, I'm not sure how that could be (if they are definitely your parents!), are there any geneticists here with an explanation?

8. hmmm

9. I've been thinking about this, O is never the "dominant" gene is it. It doesnt matter which DNA strand either gene is on, they would both be coding strands wouldnt they?

10. Uhmmm ... not sure what you are asking....

But DNA for 1 gene only works in 1 direction ... because of the promoter. So I don't know what you mean when you say the 'coding' strand. There is the template strand - and the other strand is there so that the DNA will be a stable double helix.

Dominant and recessiveness come into play because there will be two copies of the gene (that possibly have different alleles) in the genome.

11. Well I'm pretty confused right not but can we agree that that is pretty rare but not impossible?

12. What would parents blood type have to be if you had AB+ and your sister had O+?

P.S.
sorry for double post but this was a few days later and a new question.

13. Originally Posted by DaBOB
What would parents blood type have to be if you had AB+ and your sister had O+?

P.S.
sorry for double post but this was a few days later and a new question.
AO and BO and at least one would have to be +.

14. ok to me DaBob, that looks impossible.

15. One of must be A.
the other B.

More specific AO
and BO

to get combination AB is 1/4
same for the combination OO 1/4

If you're parent are A the other B all looks normal.

16. Originally Posted by Him
One of must be A.
the other B.

More specific AO
and BO

to get combination AB is 1/4
same for the combination OO 1/4

If you're parent are A the other B all looks normal.
I'm not asking how common it is once the parents are together. More what is the likelyhood of the parents blood type and then of them meeting and then of them having one O+ child and one AB+ child. How common would that be in human population as a whole? Obviously I don't expect and exact number. I'm sure it's pretty rare.

17. wikipedia blood types

Table of ABO and Rh distribution by nation
ABO and Rh blood type distribution by nation (averages for each population) Population O+ A+ B+ AB+ O− A− B− AB−
Australia[11] 40% 31% 8% 2% 9% 7% 2% 1%
Canada[12] 39% 36% 7.6% 2.5% 7% 6% 1.4% 0.5%
Denmark[13] 35% 37% 8% 4% 6% 7% 2% 1%
Finland[14] 27% 38% 15% 7% 4% 6% 2% 1%
France[15] 36% 37% 9% 3% 6% 7% 1% 1%
Hong Kong, China[16] 40% 26% 27% 7% <0.3% <0.3% <0.3% <0.3%
Korea, South[17] 27.4% 34.4% 26.8% 11.2% 0.1% 0.1% 0.1% 0.05%
Sweden[18] 32% 37% 10% 5% 6% 7% 2% 1%
UK[19] 37% 35% 8% 3% 7% 7% 2% 1%
USA[20] 38% 34% 9% 3% 7% 6% 2% 1%

18. wow that's weird... I thought O+ and - were both rare. Guess I was wrong. Anyways, thanks for finding that for me.

19. Originally Posted by Zelos
Originally Posted by leohopkins
Both of my parents have O+ blood.

I have B+ blood.
then they arent your parents, atleast not one of them and im pretty sure its your father by best guess xD
your parents can only give O gene so where the B gene come from in your case must be another guy that isnt your father, or mother

What are the odds of having an O+ blood type and having a sister with a AB+ blood type
your parents can be A and B and have the gene for for O so your sister got the A and B form your parents while you got the Os
Right, that is very true. One cannot have BB or BO if parents are OO and OO.

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