Blood type question

[value_meal_2]

Poll question of the day (but you'll have to comment since my account is not paid):

Do you know your blood type? And if so, what is it?

Me? My parents FORGOT what blood type I am. So I have no idea. My mom is AB- and my sister is B-, and I think my dad is A+ or something, so what the hell am I?

Comments

[chisaikumo]

I'm O+. If you're right about your dad, you're either A or B. If he's B, you're B. He's not A, because your sis is B. No idea about +- though. That's all I can say for sure.

Pick one and it's 50-50. =)

[miareturns]

how are you coming up with that?

[value_meal_2]

I was talking about it with some friends the other day, and I was the only one who didn't know hers. So I got curious, haha.

[miareturns]

no i was asking chisaikumo how they were coming up with all that, like "if he's b you'e b"

[value_meal_2]

Ohhhh. Whoops =)

[miareturns]

GEEZ Margie!

i keed, i keed.

[chisaikumo]

Genetics =). Or at least what I can remember from Bio AP. Her mom's AB, so she'll get A or B from her, but not both. Her dad is O, which is recessive so her blood type would take on whatever she gets from her mom. It's unlikely her dad is A (Ai or AA) because there wouldn't be a...well ok, there would be a small chance...like 12.5% (50 of having an i to give * 25 of having the right combo) of having a B-type kid. But B would have a 87.5% chance of producing a B phenotype. I only mentioned all that because she's not sure of what her dad is, but if he's O, it's 50-50. If he's not, it's something mathy, and I'm sure I'm going to fail math.

[daemonllama]

You are sorta right and sorta wrong. If her sister is B and her mom is AB, that means that his dad either has AB, AO, BO, or B blood. Since she thinks her dad is A, then if that is true he must be AO. If he is AO (which is probably the case, because O is by far the most common allele) then Margie can either be A, AB, or B. There is really no reason it is unlikely that he is A, because given that he is A he must be AO and if he is a child produced with an AB has a 25% chance of being B. You didn't need to halve the 25% because it had become a conditional probability (The outcome was B, given that outcome, he could not have been AA and there for the chances of that outcome having occured are actually 25%). The +- thing would be 50-50 if her father is +/-, 100% + if he is +/+. If he is A0 then Margie has a 50% chance of being A, and 25% of being either AB or B. I hope i explained the conditional probability thing in a way that made sense.

[chisaikumo]

Whoa, I could have sworn it said O for her dad. Maybe she checked, in which case we were both right/close. =)
Although I didn't take into account that O is most common despite being recessive, or that AA isn't a possibility anyway. It's been well over a year since Bio AP.

[value_meal_2]

It used to say O for dad, but I asked him and he said it was A, so I edited the post. Sorry! Haha