Punnett Square Calculator , Formula, Calculation & Example

Punnett Square Calculator

How does inheritance of traits work? This calculator, the Punnett square calculator, will help you answer these and other questions. This calculator is useful if you need to determine the genotypic and phenotypic ratio or if a chart of dominant and recessive traits is needed. Our Punnet square maker allows you to calculate the likelihood of inheriting rare or recessive genetic disorders.

Perhaps you are looking for an Punnett Square calculator with 2 traits and 4 alleles or an extreme three-trait Punnett square generator?

This Punnett square generator will show you the basics and guide you step-by-step on how to make your own genetic square. Continue reading!

How to make a Punnett square Examples

It is very easy to create a 1 trait gene chart. To create a Punnett Square, not all genes can be used. Here are some guidelines to help you get started:

  • These traits have to be inherited separately (their genes cannot be found in close proximity in the genetic material).
  • External factors can’t influence the inheritance of a particular gene.
  • Only the alleles that we use in the genetic square can define a trait.

The inheritance is a great example of a trait that can be used in the Punnett square calculation.

The height for a child can’t be predicted by the Punnett square method because there are too many variables that affect this trait.

Genes, or the memory banks of a cell, can transmit traits to other cells. There are two versions of every gene, known as alleles. dominant alleles are written in capital letters (A) and recessive alleles are written in lowercase (A). Dominant alleles have a higher strength. The trait it carries will always remain visible if the dominant allele is present. If there are not dominant alleles, the recessive alleles will be invisible.

If you know your blood type, why not check to see if you can donate it?

Punnett square calculator in practice

Let’s suppose we want to know how likely it is that our patients’ babies will inherit a genetic disorder called Cystic Fibrosis.

  1. Learn more about inheritance.

Autosomal recessive. Autosomal inheritance refers to the fact that the described genes are found on regular chromosomes [1-22], but not sexchromosomes (X,Y em].

  1. Learn about the genetics of your parents.

Both parents have children with cystic Fibrosis. Although both parents are in good health, they may still be carriers of cystic fibrosis because the disorder is autosomal recessive.

  1. Complete the square This case requires two Punnett squares.
  • A – Healthy, dominant allele
  • A – Recessive allele for Cystic Fibrosis

First Situation: Both parents are carriers.

♂️\♀️ A a
a Aa aa


Cystic fibrosis is possible in 25% of cases.
These parents are likely to have 75% health among their children. Of those, 2/3 will be carriers and 1/3 won’t inherit any cystic fibrosis genes.
(If the percentages are confusing, you can use the percentage tool.

Second Situation: Only one parent can be a carrier.

♂️\♀️ A a


This situation will ensure that 100% of the babies are healthy. 50% will inherit an incorrect allele that makes them carriers.

Play with our Punnett square calculator to explore all possible options.

The phenotypic and Genotypic ratio

Phenotype is the appearance of what’s visible. Genotype is hidden genetic characteristics of a trait.
What is the difference? It matters.

Let’s take a look at the below genetic table.

♂️\♀️ A a
a Aa aa

Let’s now calculate the genotypic as well as phenotypic ratios.

Result Genotype Phenotype
Aa Aa A
aa aa a

Genotypic ratio

  • AA : Aa : aa = 1 : 2 : 1

Phenotypic ratio

  • A = a = 3: 1

Allele is recessive and when it appears alongside a dominant allele, it does not display the trait it carries. However, the allele is still present and can be inherited in future.

Autosomal alles – homozygous, heterozygous, or autosomal?

These are the basics that may be important for proper use of the gene calculator.

  • Homozygous dominant is a set of genes that describes a specific trait. This concept can be used when both the dominant and auxiliary alleles of a gene are present ( AA).
  • Homozygous recessive We use it when both described alleles ( and aa are recessive).
  • Heterozygous We use it when one allele recessive (a) and the other dominant (A).

Mendelian inheritance

Gregor Mendel, a simple experimenter on garden peas, created the basic rules of genetics in 1865. In that time, there was no scientific technology or microscopes. He was able to draw useful conclusions using simple experiments and insightful observations. It’s not surprising that he is called The Father of Genetics.

  1. Traits can be unitary (red color vs. Yellow color).
  2. Every gene has two versions (now called alleles).
  3. There are some alleles that are more dominant than others (dominant aleles).
  4. Alleles are randomly segregated.
  5. There is no guarantee that either one of the two alleles will be inherited.
  6. Genes can be inherited by themselves.

We can now say, a few centuries later that Mendel was wrong – some of the genes are inherited together because they are so close to each other on the chromosome. Some of the genes are codominant, which means that two dominant alleles may coexist and show up in the phenotype. This is evident in blood types inheritance, where dominant alleles A (and B) work together to create the AB blood type.

Types of Punnett squares

The Punnett square maker is able to make autosomal alleles (chromosomes 1- 22), but can also be used for other purposes.

Let’s look at Xlinked diseases. These are disorders that can only be inherited from the female line in the family. Each woman inherits two different X-chromosomes from her parents. One of the X chromosomes may be faulty or sick and the other, healthier, can take over. Each man is born with one X chromosome. Only one wrong allele can cause disease in men, but not in women.

Hemophilia, which is rare and X-linked, is a genetic disease. We are interested in knowing the odds that a hemophiliac male will have a child with this disorder. His partner is healthy and there are no signs of hemophilia in their family.

  • XD – HealthyX chromosome
  • Xd – Hemophilia gene with X chromosome;
  • Y – The Y chromosome.
    ♂️\♀️ XD XD
    Xd XdXD XdXD


    It is clear that all the children of the patient will be healthy. However, could transmit the disease to the next generation. His sons will all be free from the disease.


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