3 Georges blood type is A Marthas blood type is B Both Georg

3. George’s blood type is A+. Martha’s blood type is B+. Both George and Martha had a parent had type O-blood. George and Martha have a kid. What is the possibility that the kid has a blood type of O-?

Solution

Answer: Possibility of “O-“ is: 1/16 or 6.25%

Since the genes responsible for blood group type (A, B, AB and O) and Rh factor (+ or -) are different and independently distributed to the future generations, we also need to solve this problem separately with respect to blood group and Rh factor.

Blood Group:

George blood group is A: Genotype probability is either AA or AO (Since the “A” is dominant over “O“)

Martha’s blood type is B: Genotype probability is either BB or BO (Since the “B” is dominant over “O“)

George and Martha’s blood group is O: Genotype is OO (Since the “O” is recessive over “A” and “B”)

Since the father’s blood group genotype is OO,

Rh Factor:

George Rh blood group is “+”: Genotype probability is either “+ +” or “+ -“ (Since the “+” is dominant over “-“)

Martha’s Rh blood group is “+”: Genotype probability is either “+ +” or “+ -“ (Since the “+” is dominant over “-“)

George and Martha’s Rh blood group is “–“: Genotype is ” - -“ (Since the “-” is dominant over “+“)

Since the father’s Rh blood group genotype is ” - -“,

Now, we will draw punnet square separately for blood group and Rh factor prediction

Blood Group distribution to the kid:

George

A

O

Martha

B

AB

BO

O

OA

OO

Probability of “O” group: 1/4

Rh factor distribution to the kid:

George

+

-

Martha

+

++

+-

-

-+

--

Probability of “-” group: 1/4

Probability of “O-“ is: ¼ x ¼ = 1/16 or 1/16 x 100% = 6.25%

So Probability of “O-“ is: 1/16 or 6.25%