Help your students develop a true understanding of the principles of sex-linked inheritance.

A pedigree is presented with a trait determined by a recessive sex-linked gene.  The student has to fill in all the genotypes in the pedigree.  A sample pedigree is shown, including a template of all chromosome types, the instruction window, and a trash can for discarding chromosomes:

The first genotypes that have to be assigned are those of the founder individuals.  The chromosomes for these have to be dragged from the template box:

Any individual whose parents are shown in the pedigree inherits chromosomes from the parents. In this way the rest of the pedigree is filled out.

The student then checks to see if the answer is correct:

Unfortunately, there is an error:

Clues help students identify what is wrong:

The program is strict on requiring that each chromosome can be definitely inferred. Changing the first individual gives:

The value comes in repeating the exercise a number of times for different pedigrees, with each repetition reinforcing the principles of sex-linked inheritance:

At the end of the exercise students get to see how long it took them to complete, and how many mistakes were made. This is the current record that we know of.  Teachers can ask students to record this information and use it to direct their attention in class room time: