Genetics – Lop Ears

This worksheet allows students to practice doing genetic crosses that involve two traits. The first problem has the 4×4 Punnet square already set up. Once they fill out the square, they determine how many of the bunnies have floppy or long ears, and how many have black or pink noses.

Note, these genetic traits are fictional, though some breeds of rabbits have floppy ears, the trait is controlled by complex interactions of multiple genes.

On page two of this exercise, students explore traits in fruit flies, such as vestigial wings and sepia eyes. Sepia eyes is a brown color, whereas red eyes are the wild-type version. The sepia eye gene is not sex-linked and not located on the same chromosome as the vestigial wing gene. This means that the heterozygous cross students complete will result in a 9:3:3:1 ratio.

Fruit flies with this mutation are often used in laboratory genetic studies. Flies with vestigial wings are easy to contain (they don’t fly!) and the phenotypes are easy to view with a hand lens. You can even order a culture of vg se flies from Amazon to show your students.

fruit flies
Drosophila melanogaster with sepia eyes and vestigial wings compared to wild-type with red eyes and normal wings.

HS-LS3-2 Make and defend a claim based on evidence that inheritable genetic variations may result from: (1) new genetic combinations through meiosis, (2) viable errors occurring during replication, and/or (3) mutations caused by environmental factors.