Heredity slides and Questions

What is the difference between a Punnet square and a pedigree?

So we know that they don't sound the same, but why? Because punnet squares give us information about the offspring, while pedigrees are diagrams that allow us to visualize patterns of inheritance throughout a family's history.

Is it a girl or a boy in your pedigree?

You already know the definition of a pedigree, which is that it tracks a specific trait throughout many generations of a family. But did you also know that they can track genders too? A square resembles a male and a circle represents a female. Have you watched Spongebob? Then you will get this trick. Spongebob is square, and Mrs. Puff is a circle. Remember that to help you remember how to do a pedigree!

​Shading in a pedigree

So you can track traits in a pedigree. But how? Well, with shading of course! If the person is not shaded, then they do not carry or show that trait. If it is half-shaded, then they carry the trait. And if it is fully shaded, then they show the trait.

Alleles

A dominant allele means that it starts with an uppercase letter. Ex: the T in Tt. A recessive allele means it starts with a lowercase letter. Ex: the first t in tt. These are what you use to make a punnet square. Homozygous is when the alleles are identical. Heterozygous is when they are different. Both TT and tt are homozygous. Tt is heterozygous. Remember "homo" means one. One kind of allele.

​Phenotypes

What are phenotypes you ask? Well, they are how you look. Think phenotypes start with P, and so does physical, or physical appearance. Emersyn's hair phenotype is brown, and Anabelle's eye phenotype is hazel. As long as you remember that phenotype is physical, you'll do good!

Genotypes

Now what is different about genotypes than phenotypes? Genotypes are extremely similar to an allele. But this time, they are in pairs. Tt is a genotype. It is a heterozygous genotype, which you learned a couple of minutes ago. It will never be written tT.

​How to make a punnett square

Is there a proper way to write the punnett square? Yes, there is! The mom's genotype goes on the side. The father's genotype goes on the top of the punnett square. Each of the small squares in the punnett square is 25%.