ELi5: how can a single fertlized egg/cell produce a full body with so many different cell types? are we talking about extracting a compressed file or making factories which has different products to produce?


ELi5: how can a single fertlized egg/cell produce a full body with so many different cell types? are we talking about extracting a compressed file or making factories which has different products to produce?

In: 22

A bit of one, a bit of the other.

A zip file is an excellent analogy for DNA by the way, so yes, everything starts with the extraction of the data.

To answer the other part of the question, the cells that make up an early embryo are ‘undifferentiated’. They’re basically all the same and have no specialist roles, what we popularly call ‘stem cells’, but can be persuaded by the instructions within DNA to become specialised. Some will become skin, others parts of organs, bone, basically whatever is required to build a person.

Every single cell contains a full copy of the code needed to make any type of cell found in our bodies. (I must admit I don’t know what the triggering mechanism is that decides what any given cell is going to be)

Edit: Almost every cell. Eggs and sperm carry only half of the code-base and must be paired to produce a full script (and a human being)

Tl;dr it’s a bit of both. Or you can watch [this](https://www.youtube.com/watch?v=ydqReeTV_vk)

It’s a bit of both. Almost all your cell contains all the data needed to make a perfect biological clone of you, if the cloning machine was perfect.
The same happens with the egg. It has all the data in it, now it needs to build it. So, taking all the nutrition from the mother, it starts building. The cells divide and take on different roles. There are roles like becoming organs, or signaling other groups of cells on what to do and what not to do. So some become factories which will make products like blood and stuff, others will become the organs themselves.

Your DNA has the instructions for every cell type stored on it. Depending on what cell type is needed your body uses certain parts of it.

Your DNA is compressed in a literal sense, not in a computer file sense. It’s basicly rolled up in it’s base form. The cells can unroll specific parts of it to read certain data.

Genes can also be turned on or off by placing certain markers on it. This way what information is read is regulated by your body and it can produce all these cells.

Factory works surprisingly well as an analogy.

Think of your DNA as the blueprint for your entire body. The fertilized embryo is essentially a command centre that tells the factory how to expand.

We want to build a human that does human things, so walking, breathing, thinking, and for that we need legs, lungs and brains. So the command centre “expands” (duplicates) and gives a copy of the blueprint to the duplicate and tells it ‘go and build a leg’ or brain etc. Essentially it is told to only work on a specific section of the blueprint. The rest is crossed out and none of its concern.

The command centre working on the leg eventually splits into command centres working on the veins, the muscles, the skin, etc, much like how in a building multiple different companies will install water and electricity, and the entire building itself of course.

Nevertheless, all of this starts with one command centre and relies on this one blueprint: Your DNA

The command centres are your so-called stem cells. Now, I should note that this seems to imply that there is one queen stem cell from which you grew, a central command centre, but this is not the case. Instead of giving out tasks which slowly grow independently, the first phases of your life you are just a clump of stem cells that can be anything.each of those then proceeds to become the sections of your body and lose their versatility, but no original stem cell can be pointed out.

The mechanism you’re looking for is [transcription factors](https://en.wikipedia.org/wiki/Transcription_factor). Depending on what signals a cell receives from outside, it may transcribe a protein that binds to different sections of DNA, either enhancing or inhibiting transcription of that piece of DNA.

This is an area of research that will probably take decades to fully unravel. We don’t know how many kinds of tissue there are in your body. Thousands? Every one of them has gone through multiple rounds of differentiation. (Except egg cells; obviously they don’t differentiate.)

My favorite example is [FOXP2](https://en.wikipedia.org/wiki/FOXP2), a gene that’s found in many species, but the human version is unique. We’ve known for a long time that FOXP2 has something to do with our ability to make language, but it wasn’t until fairly recently that we knew how.

I was about to write a bunch of stuff about the history of what we’ve learned about this transcription factor, but the Wikipedia article says it all better than I ever could. This is a *very* deep wiki-hole, so if you’re susceptible to those, be careful. 🙂

Happy learning!

Plenty of good answers, but I will try for a short and simple one:

1. Every cell contains full “blueprint” in its DNA, i.e. building instructions for entire body.

2. Cells can replicate, i.e. make copies of themselves (as long as they have access to nutrients).

3. Cells start out all same, but can specialize into types if conditions are right. Normal foetus development does create those conditions.

4. Cells can “communicate and coordinate” with each other, using chemicals (hormones) rather than nerves.

So cells replicate, specialize and arrange themselves according to the instructions in the DNA.

It still sounds like an very complex task to build a human body, and it is. Plenty of things can make it go wrong, e.g. drug use by mother, gaps in nutrition, or even foetus having a blood type that is mismatched with the mother.

If you want an analogy, it is a like having the last (or first) couple on Earth rebuild the society by having children, and having those children learn new professions. Except that everybody already has knowledge of every profession, and how the society should work. In fact, the Civilization game could be an even better analogy: you start with a single stone-age person, and end up with a modern civilization.

all you have to do I implant the egg with semen then culture the specimen in the tube then from there you genelogicly pick and pull DNA strands to fit your preferences from there you’d incubate the embryo until term,

kinda like the matrix or other scifi cinematics and from there you can grow said human “clone” or hybrid, whichever you prefer

a term is normally 12 – 16 weeks

but youd need a setup to do it in