Here’s some quotes from George in Paul Duncan’s book that give important context:
“This is the cosmology. The Force is the energy, the fuel, and without it everything would fall apart. The Force is a metaphor for God, and God is essentially unknowable. But behind it is another metaphor, which fits so well into the movie that I couldn’t resist it. Midi-Chlorians are the equivalent of Mitochondria in living organisms and photosynthesis in plants - I simply combined them for easier consumption by the viewer. Mitochondria create the chemical energy that turns one cell into two cells.”
“I like to think that there is a unified reality to life and that it exists everywhere in the universe and that it controls things, but you can also control it. That’s why I split it into the Personal Force and the Cosmic Force. The Personal Force is the energy field created by our cells interacting and doing things while we are alive. When we die, we lose our persona and our energy is assimilated into the Cosmic Force. If we have enough Midi-Chlorians in our body, we can have a certain amount of control over our Personal Force and learn how to use it, like the Buddhist practice of being able to walk on hot coals.”
“The Jedi will train you to connect to your Personal Force, and then to connect to the Cosmic Force. You don’t have much power to control the Cosmic Force, but you can make use of it.”
And about the Whills and Anakin’s origins:
“The Whills are a microscopic, single-celled lifeform like amoeba, fungi, and bacteria. There’s something like 100.000 times more Whills than there are Midi-Chlorians, and there’s about 10.000 times more Midi-Chlorians than there are human cells. The only microscopic entities that can go into the human cells are the Midi-Chlorians. They are born in the cells. The Midi-Chlorians provide the energy for human cells to split and create life. The Whills are single-celled animals that feed on the Force. The more of the Force there is, the better off they are. So they have a very intense symbiotic relationship with the Midi-Chlorians and the Midi-Chlorians effectively work for the Whills. It is estimated that we have 100 trillion microbes in our body and we are made up of about 90% bacteria and 10% human cells. So who is in service to whom? I know this is the kind of thing that fans just go berserk over because they say, “We want it to be mysterious and magical”, and “You’re just doing science.” Well, this isn’t science. This is just as mythological as anything else in Star Wars. It sounds more scientific, but it’s a fiction. It’s saying there is a big symbiotic relationship to create life, and to create the Force, but if you look at all the life-forms in the universe, most of them are one-celled organisms. I think of one-celled organisms as an advanced form of life because they’ve been able to travel through the universe. They have their own spaceships - those meteorites that we get every once in a while. They’ve been living on those things for thousands of years, they’ve been frozen, unfrozen, and can survive almost anything. The one-celled organisms have to have a balance. You have to have good ones and bad ones otherwise it would extinguish life. And if they go out of balance, the dark side takes over.”
“The Midi-Chlorians started the birth process in Anakin’s mother. The Whills communicated the command to the midi-chlorians, which activated the DNA that germinated the egg. That’s why Anakin doesn’t have a father. He was in a bizarre and metaphorical way touched by God, but in this case they happened to be one-celled animals.”
As well as an older article from Jonathan Rinzler clarifying that it’s not at all about blood:
https://www.starwars.com/news/so-what-the-heck-are-midi-chlorians
I honestly think one of the most unfortunate things to happen with Star Wars is that we’ll probably never know the full story of these story points George planted to explore further in his Sequels. I honestly would like to hope having the full story laid out between this and the mystery of Sifo-Dyas being resolved that the Prequels would be understood more so at the very least as I think having certain story points and the apparent “plot holes” resolved would truly show the scope of the consequences of our actions and dilemmas faced by a family across generations.