SpongeBob dihybrid practice with answer keys? The cross RR X Dd is showing two different genes for the parents (it is showing RR for one parent and Dd for the other) - therefore this is not a dihybrid cross. However, if it was RRDd X RRDd[PDF] Bikini Bottom Dihybrid Crosses Answer Key Bikini Bottom – Dihybrid Crosses Purebred roundpants, heterozygous long nose _ssLl_____ 4. SpongeBob’s aunt, who is a roundpants, has a cute stubby nose. She has finally found the sponge of her dreams and is Answer the questions based on your Punnett square.