Simplify the following text for a Grade 6 native English-speaking person.
Original: Each plastid creates multiple copies of the circular 75 â `` 250 kilobase plastome . The number of genome copies per plastid is flexible , ranging from more than 1000 in rapidly dividing cells , which generally contain few plastids , to 100 or fewer in mature cells , where plastid divisions has given rise to a large number of plastids .
Simplified: A plastome is the DNA genome of a plastid .