Simplify the following text for a Grade 6 native English-speaking person.
Original: Mew 's number in the National PokÃ dex is 151 , the last of the first-generation PokÃ mon , with 150 being Mewtwo and 152 being Chikorita .
Simplified: Mewtwo is a `` Genetic '' species of PokÃ mon that is number 150 in the PokÃ dex .