Why was finding a close relationship between mitochondrial DNA and bacterial DNA considered particularly strong evidence in favor of the endosymbiosis theory?

Video transcript

Hello everyone here's our next question. Which of the following correctly represents the similarity between mitochondrial DNA and bacterial DNA. That provides evidence for the endo symbiosis theory. So let's recall from our content videos what the endo symbiosis theory is. It's a theory about the evolution oops of you carry outs that says that they arose when their ancestral cells absorbed the ancestors of mitochondria and chloroplasts. And that this absorption allowed a mutual ist IQ. Or mutually beneficial relationship where the absorbed ancestor cells the mitochondria and chloroplasts provided a new source of energy for those eukaryotic ancestor cells and the eukaryotic ancestor cells provided a beneficial environment shelter for the precursors of the mitochondria and chloroplasts. So mutually beneficial relationship between those two leading to the evolution of eukaryotic cells. So a lot of the evidence behind this has to do with similarities between mitochondrial cells mitochondria. I'm sorry. And chloroplasts and bacteria specifically. This question is asking us about similarity between mitochondrial D. N. A. And bacterial DNA. That helps provide some of this evidence. So let's look through our answer choices. Choice A says they have the same genome length. Well this is not correct mitochondria have a much shorter genome then um bacteria do. That's because mitochondria don't need to exist independently. So very early on in their evolution a bunch of genes that were not necessary disappeared. So they have a much shorter genome than bacteria do. Makes sense because bacteria have to exist on their own. They need more genes than the mitochondria do. Choice. B says they have many conserved DNA sequences. Again not correct. There was a lot of gene loss very early on in that evolution, Choice C says they have accumulated the same genetic mutations. Not correct again you wouldn't expect that um the lines between bacteria and mitochondria if this is the correct path of evolution diverged so long ago um that they wouldn't have accumulated the same mutations because they've been evolving independently since then. So Choice D. Is all that's left. It says they have circular and single stranded DNA. And this is correct. This is a similarity between the D. N. A. Of both. And this is good evidence for this endo symbiosis theory because mitochondria dwell within eukaryotic cells. Well the eukaryotic cells have different DNA. Their D. N. A. Is linear and double stranded. So the mitochondrial DNA being circular and single stranded is significantly different. But they are similar to the D. N. A. Of bacteria. So that's a pretty good source of possible evidence for that Endo symbiosis theory. So which of the following correctly represents the similarity between mitochondrial DNA and bacterial day and D. N. A. Providing evidence for endo symbiosis theory. That's choice D. They have circular and single stranded DNA. Thanks for watching. See you in the next video