Blood type Punnett square practice

Twelve practice problems on ABO and Rh inheritance. Pick every blood type the child could have, check your answer, then open the worked square.

Score: 0 / 0 checked · 12 problems

Problem 1ABO
A heterozygous type A mother and a heterozygous type B father. Genotypes: AO × BO. Which blood types can their children have?
Worked answer
AOBABABBOBOAOAOOO
Genotypes: AB 25%, BO 25%, AO 25%, OO 25%
Blood types: AB 25%, B 25%, A 25%, O 25%
Problem 2ABO
A homozygous type A parent and a type O parent. Genotypes: AA × OO. Which blood types can their children have?
Worked answer
AAOAOAAOAOAOAAOA
Genotypes: AO 100%
Blood types: A 100%
Problem 3ABO
A type AB parent and a type O parent. Genotypes: AB × OO. Which blood types can their children have?
Worked answer
ABOAOABOBOAOABOB
Genotypes: AO 50%, BO 50%
Blood types: A 50%, B 50%
Problem 4ABO
Two type A parents who both carry O. Genotypes: AO × AO. Which blood types can their children have?
Worked answer
AOAAAAAOAOAOAOOO
Genotypes: AA 25%, AO 50%, OO 25%
Blood types: A 75%, O 25%
Problem 5ABO
A homozygous type B parent and a heterozygous type A parent. Genotypes: BB × AO. Which blood types can their children have?
Worked answer
BBAABABABABOBOBBOB
Genotypes: AB 50%, BO 50%
Blood types: AB 50%, B 50%
Problem 6ABO
Two type AB parents. Genotypes: AB × AB. Which blood types can their children have?
Worked answer
ABAAAAABABBABABBBB
Genotypes: AA 25%, AB 50%, BB 25%
Blood types: A 25%, AB 50%, B 25%
Problem 7ABO
A heterozygous type B parent and a type O parent. Genotypes: BO × OO. Which blood types can their children have?
Worked answer
BOOBOBOOOOBOBOOO
Genotypes: BO 50%, OO 50%
Blood types: B 50%, O 50%
Problem 8ABO
A type AB parent and a heterozygous type B parent. Genotypes: AB × BO. Which blood types can their children have?
Worked answer
ABBABABBBBOAOABOB
Genotypes: AB 25%, BB 25%, AO 25%, BO 25%
Blood types: AB 25%, B 50%, A 25%
Problem 9Rh
Two Rh-positive parents who both carry the Rh-negative gene. Genotypes: Dd × Dd. Which blood types can their children have?
Worked answer
DdDDDRh+DdRh+dDdRh+ddRh−
Genotypes: DD 25%, Dd 50%, dd 25%
Blood types: Rh+ 75%, Rh− 25%
Problem 10Rh
A homozygous Rh-positive parent and an Rh-negative parent. Genotypes: DD × dd. Which blood types can their children have?
Worked answer
DDdDdRh+DdRh+dDdRh+DdRh+
Genotypes: Dd 100%
Blood types: Rh+ 100%
Problem 11Rh
A heterozygous Rh-positive parent and an Rh-negative parent. Genotypes: Dd × dd. Which blood types can their children have?
Worked answer
DddDdRh+ddRh−dDdRh+ddRh−
Genotypes: Dd 50%, dd 50%
Blood types: Rh+ 50%, Rh− 50%
Problem 12Rh
Two Rh-negative parents. Genotypes: dd × dd. Which blood types can their children have?
Worked answer
dddddRh−ddRh−dddRh−ddRh−
Genotypes: dd 100%
Blood types: Rh− 100%

Need a refresher?

The interactive blood type Punnett square lets you pick any genotypes and watch the boxes fill. For blood types without genotypes, the blood type calculator gives the range of odds, and every parent pairing has its own page in the parent–child blood type chart.

Frequently asked questions

How do you solve a blood type Punnett square?

Write one parent’s two alleles across the top and the other’s down the side, fill each of the four boxes with one allele from its column and one from its row, then convert each genotype to a blood type: AA or AO is A, BB or BO is B, AB is AB, OO is O. Each box is a 25% chance.

What is the genotype ratio for AO × BO?

1 AB : 1 AO : 1 BO : 1 OO, so 25% each of blood types AB, A, B and O. It is the only single cross that can produce all four ABO groups.

Can I print these problems?

Yes. Use your browser’s print command. The answer key prints too if you open it first.

How do I combine ABO and Rh in one problem?

Solve each gene in its own square, then multiply the probabilities. For example, AO × BO gives 25% type O, and Dd × Dd gives 25% Rh negative, so the chance of O negative is 25% × 25% = 6.25%.