Blood type probability help with question

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#1
A woman of blood type B marries a man of blood type A. Their first child is blood type O. What is the probability that their second child will have a blood type other than O?

child 1st = 25% chance of o
SECOND KID 75% chance

I know you have to do something with those 2 percentages/probabilities but I dont know how or what to dooooo
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2 years ago
#2
The Q uses the word "blood type" [very odd] - it is known as blood group!

The ABO blood group system is inherited in a co-dominant fashion, in which A and B alleles -are dominant over O allele.

So if you draw your usual punnet square for AO and BO, you end up with the below ratios in the F1 (children)

AO - 1: group A
BO - 1: group B
AB - 1: group AB
OO - 1: group O

The given group of O for the first child has no bearing on the outcome of the group of the second child (trick Q??)

The probability of the 2nd (or any) child being NOT OO genotype [therefore not O blood group] is the probability of him/her being AO [group A] OR AB [group AB] OR BO {group B]. As all four possibilities are of equal chance, the probability of the 2nd child [AND of any subsequent child, respectively] being NOT O group is 3 out of 4 = 75%.

Is that better? Good, well done!

M
1
#3
(Original post by macpatelgh)
The Q uses the word "blood type" [very odd] - it is known as blood group!

The ABO blood group system is inherited in a co-dominant fashion, in which A and B alleles -are dominant over O allele.

So if you draw your usual punnet square for AO and BO, you end up with the below ratios in the F1 (children)

AO - 1: group A
BO - 1: group B
AB - 1: group AB
OO - 1: group O

The given group of O for the first child has no bearing on the outcome of the group of the second child (trick Q??)

The probability of the 2nd (or any) child being NOT OO genotype [therefore not O blood group] is the probability of him/her being AO [group A] OR AB [group AB] OR BO {group B]. As all four possibilities are of equal chance, the probability of the 2nd child [AND of any subsequent child, respectively] being NOT O group is 3 out of 4 = 75%.

Is that better? Good, well done!

M
Ahhh yes thank you. I annoyingly thought I had to do 0.25 x 0.75 to link them. But trick question haha
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