Well, I have a biology background too, and I didn’t find the biological business to be a dealbreaker for my enjoyment of the movie.
[spoiler]I strongly disagree that this is supposed to be a hard sci fi movie. A lot of inexplicable stuff happens - temporal, biological, spatial - and some of the characters grope to describe the weirdness they see, with the goal of making clear to the audience that ShitJustGotReal. Showing plants that grow flowers from different plant families, deer with flowered antlers, etc., primes you for changes to start happening with the characters. The description of HOX genes, ‘constant mutation’, etc, to me, just indicate that something is happening, but don’t explain how or why. ‘Refraction’ is as good a word as any to describe an eerie blending process that, yes, should be biologically impossible. I think that the characters know it is impossible, too. Lena says as much. It should also be impossible to catch someone else’s tattoo or speech patterns or have your house show up duplicated in a swamp. They leaned heavy on the biology, cause you get to have some Cronenbergian body horror that way, but there was physics ‘horror’ going on too. I wonder, if the physicist had said that the atomic clocks were running backwards or that the gravity was reflecting too slowly, would it have put you off so much?
I don’t mind that Lena had a magic microscope, like I don’t care that Luke has a magic laser sword. As for the cells dividing before her eyes - it’s to show the viewer that the characters are already affected, even if they look normal. If it was an RBC, nice and red, it shouldn’t divide anyway - no nucleus and terminally differentiated. So maybe it was an immature WBC that squeaked out of her marrow a bit early, or whatever. It also happens way too fast to be real-time. Would the movie have been better if the sequence took half an hour, in a well-lit lab, with power supplies humming away and a full suite of slide preparation equipment and stain baths? An RBC from a drop of her blood shouldn’t be able to spin up into a creepy genetic duplicate, either - no genome, recall.
"We’re left with no clue about what the rules of this universe were, or why anything happened the way it did. " I think that that was kind of the point of the whole movie, actually. They have some sciency-sounding descriptions for the effects they see, but no understanding of the mechanism or purpose, and I think that’s intentional. The book makes clear, and I think that the movie tries to show, that the Southern Reach organization is demoralized and confused by their continual inability to figure out just what the fuck is going on in the Shimmer. It has been three years, and now the only volunteers going in are self-destructive obsessives. The explorers are professionals who try to explain things based on their areas of expertise, like the blind men examining an elephant. Their explanations, by necessity, will be fragmentary and wrong. Their analogies will be forced. The movie wasn’t trying to say ‘Actually, a seven-dimensional intelligence from a parallel universe intersected with Earth as a result of a boom-tube failure, and its attempts to free itself caused local entities’ waveforms to chaotically interfere due to impinging tachyon fields, until the radiative flux from the burning phosphorus provided enough energy at 3230 Angstroms to catalyze the hemitranslation of the orbifold. Thank God we figured it out before the nuclear reactor in the Sun was quenched’. It was trying to say ‘Here’s an unfathomable mystery. What kind of people try to deal with that, and what happens to them?’
Anyway, de gustibus non est disputandum. [/spoiler]