Just when you didn’t think you needed another Punnett square worksheet, I present “Skinny Pig Genetics!” Hairlessness in guinea pigs is a recessive trait. Individuals with this trait have no hair on their bodies (though they do have some on their feet and noses).
This is a very basic worksheet that starts with a chart showing the genotypes and phenotypes of the guinea pigs. Students will fill in the genotypes for the heterozygous and recessive pigs. They can refer back to this chart in the second section.
There are four problems to solve. The problems include descriptions such as “a skinny pig crossed with a heterozygous one.” They complete a Punnett square to determine the ratios in the offspring.
This can be a simple way to introduce genetics and talk about guinea pigs. Who doesn’t love guinea pigs! I show them photos of different types of guinea pigs, they come in short hair, long hair, and hairless. They also have a wide variety of color patterns, but coat color genetics is another story and doesn’t follow simple Mendelian genetics rules. For more information on guinea pig coat colors, Squeaks & Nibbles offers a simple write-up and explanation.
This worksheet can be given with a variety of other practice sets on Mendelian genetics. You could also use it as a stand-alone quiz or pre-test. Over the years, I’ve noticed a lot of variation in what freshman students know about genetics. Most of my freshman this year have never seen a Punnett square, so I plan to do more basic level crosses this year.