How the first multicellular organisms modified their DNA to build both cells and not just 1

Question

So I’ve been enjoying videos from Kurzgesagt and one in particular points to the valuable molecule ATP and I remember it from biology (https://youtu.be/QImCld9YubE). So while this talks about the very beginning of multicellular organisms I’ve never understood how an organism can absorb another and then make DNA so both organisms are created going forward.

In: 1

Answer 1

I’m assuming you’re asking about the endocytosis theory for the origination of mitochondria and chloroplasts. Both mitochondria and chloroplasts have plasmid DNA, which is a circular DNA molecule that bacteria and other prokaryotes use instead of the linear DNA molecules eukaryotes use. Each plasmid has something called an origen of replication, which is a gene that control replicating that plasmid. The origins of replication in both mitochondria and chloroplasts are unique to those organelles, and don’t work with the same DNA replication machinery we use to replicate our DNA. Instead, the mitochondria and chloroplasts take care of DNA replication themselves!

So, short answer, the original organisms wouldn’t replicate both sets of DNA!