One of the best things I've read recently (wish I could find it again) said that quantum mechanics isn't about reality, it's a model of what we can measure and study. We simply can't know what reality is like at atomic and subatomic scales, we can only model what the measurements say. It turns out we can do a lot of really impressive science with those models (nuclear power, semiconductors, lots of other stuff), but acting as if we know what's actually going on at those levels is fooling ourselves. Even the people who laid the foundation for modern quantum theory knew this:

Bohr once commented that a person who wasn’t outraged on first hearing about quantum theory didn’t understand what had been said.

Heisenberg, when asked how one could envision an atom, replied: “Don’t try”

• A Short History of Nearly Everything

So what does this have to do with your question? Well, I'm not saying that fundamental reality does not exist at subatomic scales. But I am saying that we can't really know anything about that reality until we measure it.

Did the electron have its spin at creation, or at measurement? We can't really say, and it's not especially important.

A bit of a tangent: we don't fully understand quantum entanglement over distances (e.g., the fact that we can know the spin of one particle from another entangled particle's spin even over great distances), but the explanation I like is that both particles' states are just the propagation of their combined wave equation since they were first entangled. So were their spins assigned at entanglement or at measurement? Well, we don't know and it's not a meaningful question because we can't determine the answer without measurement.

Your chromosome analogy doesn't really work because your chromosomes are a classical system. They have been entangled with countless other molecules for as long as they have existed, so we can use our human intuition to reason about their past and future in ways that we can't reason about things at quantum scales.

Maybe give it a second watch. Your proposal is literally what Einstein suggested, and what Bell's experiment disproved.

Even if my parents never observed me, I would still be a boy.

Technically, quantum mechanics says no. This is the Schrodinger's Cat situation.

What happens if a particle doesn't get observed, does it not have spin?

It is said to be in a superposition of having both spins. It collapses to one spin when observed.

Electron and positron* not proton.

He explains in the video why the particles can’t have local hidden variables. I suggest you watch a video specifically about local hidden variables and Bell’s theorem.

It sounds like you're asking why local hidden variables can't explain the experimental results? But a huge part of the video is spent explaining this so I'm assuming that isn't what you mean. So I'm not sure what it is exactly that you're asking. Could you elaborate on how what you're suggesting differs from the local hidden variable explanation?

ETA: I think you are asking about hidden variables but maybe don't realize it because it was brushed over in the video. When she's discussing the possible strategies for how the particles would decide their orientation, she says there are only 2 strategies that work. Your strategy is one that doesn't and here's why I think that is.

Say your electron is created with 0 degree spin. When deflected with a 0 degree detector, the electron goes up and the positron goes down 100% of the time. Great. But what about the 120 degree detector? Well the electron goes up 3/4 of the time and down 1/4. The positron goes up 1/4 and goes down 3/4. But this can't be. If the electron goes up, the positron must go down. So in order for it to work, they'd need to pick one of the strategies she talks about in the video. They need to agree on how they'd respond to each of the orientations separately, rather than just agree on a spin direction at creation.

Haven't seen the video, but can probably still answer the question.

Basically, if the experiment is set up right, it's not the obvious number you'd expect. It's as if they're passing notes to beat the measurements. (Although not enough to transmit novel information, which is another QM misconception)

If you want to understand it rigorously, this section of this article might help. Jargon is the only real thing that I can see that would be a barrier.

That's... kindof the question, isn't it?

(Disclaimer: I haven't seen the video yet. But yeah.)

That's a quantum mechanics thing. And quantum mechanics has a long history of making physicists and physics students really uncomfortable. The following two quotes illustrate just how fucked up quantum mechanics really is:

God does not play dice

• Albert Einstein

I don't like it, and I'm sorry I ever had anything to do with it.

• Erwin Schrödinger

Before quantum mechanics, our Newtonian understanding of the world was really simple. We thought particles were little billiard balls floating around and bumping into each other and being attracted and repelled by electric fields and such. But nope! Turns out you can't even conceptually understand what's going on at that scale without making the observer/measurer/measurement a central feature of the literal math. But if you don't do the uncomfortable things in the math, you can't get results from the math that match what happens in the real world.

W.

T.

F.

Seriously. You're asking exactly the right question. The question that made the discoverers of quantum mechanics uncomfortable in the first place. Unfortunately, there's no one answer to it. There are a bunch.

In practice, you don't really have to have "the answer" to that question to design functioning solid-state storage devices or predict the half-life of a muon. You can just kindof throw up your hands and take it for wrote that "the spin doesn't exist until it's measured" (nor the position nor the velocity nor any of a bunch of other such properties of the particles in the system). But it's not like physicist don't still have this question in the back of their minds keeping them up at night.

Gender isn't chromosome dependent =D

Disclaimer: I'm probably oversimplifying it

The best way i can describe it is that the spin of the electron could be either, BUT when the observation is made, you now exist in one of the possible universes where it you and it are now entangled where it has only the spin that you observed.

This means there is (according to my lay person understanding) that after the observation there are now two discrete universes where each version of the particles exist with opposing spin.

I read it's like a pair of shoes, in two boxes, randomly mixed. If you open one box, you instantly knows if the other shoe is the left or the right one, even if it's on the other side of the universe. Before opening, you don't know which one is in which box.

Then the explanation sais it was wrong.