Cytoplasmic DNA

Animal cells also store DNA in mitochondria. Plants beside nuclear and mitochondrion DNA also have some DNA in chloroplasts.

Human mitochondria store genetic information in about 10 circular pieces of DNA. This autonomy (having own genetic information) suggests that they existed as single organisms before they got into Eucariotic cells and became organelles. Additional proof is the different DNA code. The same triplets (units od DNA code) denote different amino acids in DNA in nucleus and in mitochondria. For example UGA codes tryptofan amino acid, but not the end of translation like in nuclear DNA. Other differences are lack of introns and transcription and translation of both strands of DNA.