Dihybrid Cross Punnet Square Calculator

Created by Łucja Zaborowska, MD, PhD candidate and Wojciech Sas, PhD candidate
Reviewed by Bogna Szyk and Jack Bowater
Last updated: Aug 31, 2022

In need of a giant dihybrid cross Punnett square? Search no more! Dihybrid cross calculator allows you to compute the probability of inheritance with two different traits and four alleles, all at once. It is a bigger version of our basic Punnett square calculator.

This two-trait Punnett square will allow you to calculate both the phenotypic and genotypic ratio of the dihybrid cross. It's also the perfect place to get some basic knowledge on the construction of genetic squares and learn some inheritance rules!

How to do a dihybrid cross?

4x4 Punnett squares might be quite a challenge! There's quite a lot to deal with:

  • 16 sets of crosses in each try;
  • 9 possible versions of genotype;
  • 4 possible mother's alleles;
  • 4 possible father's alleles; and
  • 81 versions of the Punnett square!

If you want to save yourself a lot of time and hassle, we recommend you use our dihybrid cross calculator. If you're here for a challenge, follow our guidance below!

➡️ Say we'd like to know the chances that our baby will have curly and light-colored hair. The mother of the child is blonde, with curly hair, while the father has light-colored, straight hair. (You may also start with something easier – like blood type inheritance!)

  1. What are the traits we're looking for? We got two different traits: the color of the hair and the type of hair:

    • Trait A – color; and

    • Trait B – type.

  2. What is the type of inheritance? Both traits are autosomal – located on chromosomes 1-22. To simplify things, we can assume that curly and dark-colored hair are dominant traits with single genes that control them.

    Our alleles:

    • A – curly hair (dominant);

    • a – straight hair (recessive);

    • B – dark hair (dominant); and

    • b – light hair (recessive).

  3. What are the possible sets of alleles?

    • The mother is heterozygous when it comes to curly hair (A, a) and homozygous recessive when it comes to hair color (b, b). Her possible combination of alleles are: Ab, ab.

    • The father is homozygous recessive in both traits (a, a, b, b), so he produces one combination of alleles: ab.

Let's make the dihybrid cross worksheet! Remember, the size for the two-trait, dihybrid Punnet square must be 4x4!

♂️\\♀️

Ab

Ab

ab

ab

ab

Aabb

Aabb

aabb

aabb

ab

Aabb

Aabb

aabb

aabb

ab

Aabb

Aabb

aabb

aabb

ab

Aabb

Aabb

aabb

aabb

Now, since you already know how to do Punnett squares with 2 traits, you're ready to interpret the results! You can find the dihybrid cross ratio in the section below.

ps. Have you ever seen a trihybrid cross Punnett square? 🤔

Genotype and phenotype ratios

We will start with the genotypic ratio. We can either count the combinations in the Punnett square or use the dihybrid cross calculator to compute it for us. In the example presented to us in the section above, the task is really easy: 50% of the Punnet square is taken by the Aabb combination, and the other half is aabb.

It's easy to calculate that the genotypic ratio is 0.5:0.5, which is equal to 1:1.

What is the phenotypic ratio?

  • Phenotype for Aabb = Ab
  • Phenotype for aabb = ab

Now we know that the phenotypic ratio is equal to the genotypic ratio = 1:1.

In conclusion, 50% of the couple's children will be born with alleles Ab – that is, curly, blond hair. The other half will be born with alleles ab – they will inherit straight, blond hair. 👱‍♀️👱

Our dihybrid cross calculator will provide you with the percentages for the different sets of alleles. To receive the genotypic ratio, you need to divide all those numbers by the smallest percentage received, which gives you the lowest possible integer. Look at the example below:

  • 6.25 : 12.5 : 6.25 : 12.5 : 25 : 12.5 : 6.25 : 12.5 : 6.25

6.25 is the smallest number, so we need to divide everything by 6.25:

  • 1 : 2 : 1 : 2 : 4 : 2 : 1 : 2 : 1

Voila! Your genotypic ratio is ready.

If you need any help with those calculations, check out our Greatest Common Factor tool!

FAQ

How to do Punnett squares with 2 traits?

The dihybrid Punnett square can be completed in a few simple steps:

  1. Find the alleles of both the mother and the father, e.g., AaBb and AaBb.

  2. Mix. Alleles of both traits will change inside and outside of the group. For example, AB, Ab, aB, ab.

  3. Create the cross. Arrange all of the mother's mixes on the upper part of the table and the father's mixes on the left.

  4. Add the mixes of both the mother and the father and write them down in corresponding fields. For example, AB + ab = AaBb.

What's the probability of inheritance of both homozygous-recessive traits?

Let's assume that the mother is homozygous-recessive in both traits: aabb.

The probability of inheritance depends on the father's genes:

  • Double homozygous-recessive aabb; probability ~100%.

  • Double homozygous-dominant AABB; probability ~0%.

  • Double heterozygous AaBb; probability ~25%.

  • Mixed AABb, AAbb,AaBB, aaBB; probability ~0%.

  • Mixed Aabb, aaBb; probability ~50%.

What is the homozygous genotype?

Homozygous genotype occurs when two alleles (versions) of a given gene are identical.

We can distinguish:

  • Homozygous-dominant genes where both of the alleles are dominant (typically visible in offsprings), e.g., AA; and

  • Homozygous-recessive where both genes are recessive (often not visible in offsprings), e.g. aa.

What are the heterozygous genotype?

Homozygous genotype occurs when two alleles (versions) of a given gene are different, e.g., Aa.

The big letter A stands for the dominant/wild-type allele, while the small letter a informs us about a recessive/mutant one.

Łucja Zaborowska, MD, PhD candidate and Wojciech Sas, PhD candidate
Try out the smaller Punnett square calculator! 🏷

A, B - Dominant alleles

a, b - Recessive alleles
Mother's trait 1
Aa
Mother's trait 2
Bb
Father's trait 1
Aa
Father's trait 2
Bb
AABB
6.25
%
AABb
12.5
%
AAbb
6.25
%
AaBB
12.5
%
AaBb
25
%
Aabb
12.5
%
aaBB
6.25
%
aaBb
12.5
%
aabb
6.25
%
Punnett square
♂️\♀️ABAbaBab
ABAABBAAbBaABBaAbB
AbAABbAAbbaABbaAbb
aBAaBBAabBaaBBaabB
abAaBbAabbaaBbaabb
Phenotype and Genotype
ResultGenotypePhenotype
AABBAABBAB
AABbAABbAB
AaBBAaBBAB
AaBbAaBbAB
AAbbAAbbAb
AabbAabbAb
aaBBaaBBaB
aaBbaaBbaB
aabbaabbab
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