To properly build the phylogenetic tree, Julia needs information that can connect any of mentioned mammals (bear and monkey) to reptiles. And that could be only the fact that a duckbilled platypus lays eggs similarly like reptiles. So, the platypus is a mammal and relationship with bear and monkey in that way exist, but laying eggs is not characteristic for other mammals.
Messenger RNA (mRNA) molecules carry the coding sequences for protein synthesis and are called transcripts; ribosomal RNA (rRNA) molecules form the core of a cell's ribosomes (the structures in which protein synthesis takes place); and transfer RNA (tRNA) molecules carry amino acids to the ribosomes during protein.
The trait is most likely not dominant or is non recessive. For example if the female has blond hair and the male has brown and the baby has brown. The males brown hair trait was more dominant. This could later than repeat.