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Waste Not, Want Not Janet's Mystery Gene Making Magic

Janet's Mystery Gene is the twelfth episode of the second season of The Magic School Bus Rides Again. It is about genetics.

Ms. Frizzle's outfit

In this episode, Ms. Frizzle's skirt is a pattern of XY-chromosomes and double helices. Her necklace is an X-chromosome.


Carlos is assigned to read to the kindergarten class, but to his chagrin, he is given a partner who is none other than Janet, who wishes to read to the kids with a telling of her autobiography: Janet: The Untold Story Finally Told, detailing how great she is (she calls herself Janet "Awesome" Perlstein in chapter 1). Ralphie tells Janet to "have a heart", and Janet responds by turning to another chapter in her book, titled "I ❤ Me", saying "you can see it for yourself." Ms. Frizzle enters the room riding a mini-train and proposes a field trip inside Janet's heart. The other students are up for it, so they enter the Magic School Bus, with Liz staying behind with Janet. Ms. Frizzle pulls the handle on the dashboard, and the Bus converts itself into white light, phases through the window of the classroom, and shrinks to fit inside in order to approach her and Liz. Janet gives multiple warnings to the shrunken class prior to entering her body, but before she could continue, the Bus speeds into her heart.

Inside Janet, Ralphie says she does have a heart, but Jyoti points out there must be something that makes Janet the way she is, prompting Ms. Frizzle to shrink the Bus further and go deeper inside her heart. The class gets smaller and smaller and smaller until they reach Janet's chromosomes, which Ralphie points out as "mutant worms from the planet Yuck". After learning about the fact that chromosomes make up who we are, Carlos says that there must be something that makes up Janet's nervousness. The kids go inside Janet's chromosome and reach her double helices. The kids learn about the properties of DNA, from its long name (deoxyribonucleic acid) to its double-helix shape, prompting Carlos to tell everyone that a "nervous gene" might be inside this DNA. The students enter the Magic School Bus, which has transformed off-screen into the CRISPR Express (named after CRISPR Therapeutics), a train-like vehicle that is able to ride along and edit Janet's genes. As they ride, Ms. Frizzle teaches the kids about the nitrogenous bases of DNA: adenine, thymine, cytosine and guanine. Ms. Frizzle drives the Bus along Janet's DNA, as they come across genes that make up her eyes, hair, and ingrown toenail, which Arnold says runs in the Perlstein family. He shows his ingrown toenail, grossing out the rest of the class. Carlos starts the DNA editor feature on the Bus, which he thinks will change Janet's nervousness.

Impatient, Carlos speeds up the CRISPR Express, causing damage to Janet's DNA. The DNA recombines itself but causes physical changes to Janet, first her hair color from red to black, then her nose and ears, and ultimately what kind of species she is: a plant, cat, penguin, a Komodo dragon- all because of the fact that DNA has the code for anything that is living. Carlos wonders why he can't stop the Bus, and Ms. Frizzle replies that the Deaccelerator, the machine that will stop it, is currently in the auto-parts shop.

To repair her DNA, the class samples Arnold's hair and uses its DNA as a template to fix Janet. They manage to repair her but end up giving her freckles, which turns out to be a dominant genetic trait. After discovering why and repairing the mistake they return to the bus and watch the outcome. Her freckles are gone, but somehow, Janet ends up with a deep, threatening voice, because they used Arnold's DNA. They have to start over. Just as Janet enters the kindergarten classroom, transforms into a monkey, which the kids cheer in excitement at. Eventually, they completely restore Janet's code, normal voice and clear skin in all.

Carlos abandons the search for Janet's nervous gene and returns to stop Janet from reading her autobiography. Janet scolds him for being late and Carlos confesses about the mission to find her nervous gene and replace it with a nice gene, which leaves Janet non-plussed. She scoffs at Carlos, stating that a nervous gene is nonsense and that she didn't get nervous until a certain embarrassing point in her life. Carlos realizes that Janet's nervousness was simply a culmination of her experiences. Instead of her autobiography, Janet adlibs a story about Carlos, but to Carlos and the class' surprise, she manages to be nice to the kids.

Ultimately, the kids loved Janet and she is seen being chased by them, wanting to hug her. Nervous as she is, she runs from them.


  • When the class mutates Janet into an aardvark wearing glasses and carrying a book, it alludes to the titular character from the 1996-2022 PBS series Arthur.
  • The other autoparts shop is mentioned for the second time; the first was in "Gets Ready, Set, Dough"
  • This episode is the second to redesign Janet, the first being "Pigs in the Wind" from the previous season. Only one minor detail was changed - she does not have freckles, like in the fifth book, "Lost in the Solar System", and in the original 52 episodes of The Magic School Bus.
    • Janet does revert to her season 1 design when the kids give her freckles.
  • As this episode focuses on the Perlstein cousins, many things were revealed about them and the rest of their family:
    • Janet is right-handed (whilst Arnold is the opposite; shown in the producer segment of "In the Zone")
    • Arnold and Janet are lactose intolerant.
    • They are both paternally related.
  • When the class compares Janet's chromosomes to tapeworms, Wanda reveals that she also owns a cat (whom she said had worms). In "Under Construction", the Li family also owns a dog.
  • This is the last episode to focus on Carlos in this season.
  • This is the last episode to feature any of Ms. Frizzle's Class' relatives, in this case, Janet.
  • This is the last episode of the Flash/ToonBoom puppet animation era of Rides Again to focus on Janet.
  • Tim and The Talking Trees, I Spy with my Animal Eyes, and The Land Before Tim were referenced in this episode when Carlos explains his recent genetic mutations into a fir tree, fossil, and butterfly.


  • Janet's freckles are removed in this episode as a plot point, but they appear again briefly at 7:04 before Ms. Frizzle and the class begin making changes to her DNA.
  • Janet was implied not to have freckles in this episode, similar to her appearances from Gets Lost in Space to Makes a Stink. But in other episodes of this series' first season, she did have freckles.
  • When Ms. Frizzle pulls the Bus's handle to activate the Shrinkerscope, she wears the math outfit from Ralphie and the Flying Tennellis instead of the genetics outfit from this episode.