Punnett Square: A Basic Explanation for Solving

Punnett Square: A Basic Explanation for Solving

Punnett square Solving

In genetics, alleles are notated with capital and lowercase letters.  For instance, a dominant trait might be A, with a recessive trait a.  A Punnett Square will find all possible child genotypes from two parent genotypes.

For example, if the parents have Aa and aa genotypes, the Punnett square looks like this:

In each box, you write the allele from the column and row its in. This gives the child possibilities.

Possible Punnett Squares

This leads to only a couple of possible Punnett Squares. The possibilities are:
ZZ * ZZ
ZZ * Zz
ZZ * zz
Zz * ZZ
Zz * Zz
Zz * zz
zz * ZZ
zz * Zz
zz * zz

But several are mirrors of others. Of course, genes are rarely this simple. This is a good basic skill for genetics and biology, and another example of math in science.

Terms used

allele: variation or possible value for a gene, denoted by a capitol(dominant) or lowercase(recessive) letter
child: offspring when two organisms reproduce
dominant allele/trait: a trait that is shown in the phenotype even if only one allele is present, shows up in ZZ or Zz
gene: unit of heredity, trait
genotype: what alleles make up an organisms trait
heredity: passing on of traits from parent to offspring
heterozygous: containing one dominant and one recessive allele, Zz, which produces a dominant trait in the phenotype
homozygous: containing both of either dominant or recessive alleles, ZZ or zz, which produces a dominant or recessive trait in the phenotype
phenotype: actual physical appearance of a trait
Punnett Square: a figure used to determine possible child genotypes
recessive allele/trait: trait shown in phenotype only if two alleles are present, shows up in zz

Related:
Introduction to Geneticcs
Chemical Equations Quiz

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