I was looking into why chloroplasts and mitochondria have their own DNA seperate from the cells DNA. I found an interesting theory; Chloroplasts and Mitochodria were once single celled organisms. Another single celled organism consumes the mitocodria/chloroplast, but they continue to function. The cells work in symbiosis together, after millions of years the relationship has now become standard! Why do you think chloroplasts and mitochodria have their own DNA?