> Why don’t the surrounding cells say ‘hey, you’re going crazy, stop!’?

A cancerous cell might develop a mutation that would reduce the amount of a protein on it's surface that would normally be recognized by immune cells trying to kill cancerous cells.

No two cancers are exactly alike on a genetic level, even though may have the same medical label. Each is a unique collection of many mutations that lead to a cell population that can replicate, invade, evade immune detection, etc.

Very good point to make.

I think you can make a valid analogy between

DNA, biochemistry, and the physical forms of all animals and plants etc,

with

An encrypted hash (or lossless compression), the encryption/compression algorithm, and the thing that was encrypted/compressed.

The difference as you rightly point out is that we produce the hash from the desired end result 'encode' videos and images etc,

Whereas DNA evolves by the reverse process: with random hashes and if something useful emerges from that then the DNA gets kept and then adapted with more random changes that get kept or discarded.

Nevertheless, the end result is the same: a compressed/encrypted file that, with the application of the correct algorithm, can produce the entity in question. In that sense, 'encoded' is a valid verb for DNA: our physical forms are encoded within our DNA the algorithm is not reversible and never needed to be.

Cells are always having a few mutations in their DNA, but there are systems in the cell that will recognize excess mutations and kill the cell before it can cause problems.

Things can really start to get out of hand when you get mutations in those proofreading systems themselves. Then you get a set of cells that can start mutating freely. Eventually natural selection takes over and the mutant cells keep accumulating more and more mutations that help them replicate and spread, leading to cancer.

Thats about it they stop listening to the "cyclins" that regulates cell replication. This is usually quite common and the body can destroy the cells as long as theyre recognised. When they arent recognised and grow out of control it can get out of hand.

They do. Our immune system works very hard to suppress cancerous and pre-cancerous cells all over our body. The ones that become deadly tumours are the ones that by chance are able to fly under the radar of the immune system. Natural selection.

It's really hard to explain in words even in a book let alone in a few paragraphs.

Perhaps an analogy:

Langton's Ant is a mathematical curiosity. The idea is an infinite grid. The 'ant' is a marker with position and direction and gets set in motion from anywhere in any direction (the grid is infinite and uniform so it makes no difference). When the ant lands on a cell (a grid square), if the cell is white it turns it black and turns right, if the cell is black it turns it white and turns left. The future behaviour of the ant and the grid is entirely determined by those two rules and the colour-scape of the grid. No other information is present. But the picture it creates is immensely complicated.

Fractals like the Mandelbrot Set and Julia Sets could be another example.

A simple set of iterated rules can produce a very complicated structure and do so repeatedly and reliably. If you don't change the rules you'll always get the same structure.

The degrees of separation between the rules that DNA (combined with all sorts of biochemistry) provide and the physical structures they lead to are as a chasm but they are still pretty reliable and predictable so clones will reliably look almost exactly the same as each other (same rules, same outcome).

Another analogy would be trying to understand how a sequence of zeroes and ones, or the simple rules of machine code, can lead to what we can achieve even just nowadays with AI (outthinking grandmasters at Chess, generating convincing art, etc). It boggles the mind (or should). The rules of DNA (and their interaction with all sorts of biochemistry) are arguably much more complex and varied than machine code so it shouldn't really come as a surprise that it can produce an infinitude of possible biological shapes and yet do so as predictably and consistently as a computer program.

Does that make sense?

Usually it's damage to the pathway that activates this cell suicide. The body signals for it to die off but it doesn't respond to the signal. This can happen in numerous different ways, as evidenced by the multitude of types of cancers.

Edit: as an example, damage from ultraviolet light causes many cells to die off, in the form of sunburn and the blistering that follows. Some cells get mutated but don't die, and can become skin cancer.

Mutations. Those can be caused by many things, most often either DNA damage from the cell's own metabolic byproducts or mistakes made when growing/dividing cells replicate their DNA.

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What can reprogram them?

Ok thank you. So the procedure protocols can be disrupted by environmental influences eg. radiation poisoning, and by genetic, inheritable weaknesses in coding checking procedures? Why don’t the surrounding cells say ‘hey, you’re going crazy, stop!’?

On the other hand, we do talk about genes coding for stuff, so that kind of language is useful (but in a more basic manner - a gene codes for a protein, not a gene (or allele) codes for a big nose).

Your cells have, for example, some "programs" that tell them to grow and divide, and some programs that tell them to commit suicide. Those programs are normally only turned on when appropriate.

In a cancer cell, mutations cause one or more programs telling the cell to grow and divide to be constantly turned on, and the suicide programs to be broken (so even if it would be appropriate, they will not commit suicide).

There are some other programs that tend to be broken in cancer cells too, but those are two of the main ones.

Pretty much. They don't do much normal stuff beyong replication and releasing hormones that stimulate capillary growth to keep them fed.

So how does cancer work? In my mind, the cells’ programming goes AWOL and they just keep replicating and acting, regardless of procedure protocols. How true is that?

maybe a too-fine point to make here, but nothing is 'encoded' in DNA. DNA is the base level of the biological process - DNA is fed through molecular machines and the result is construction of various proteins and new molecular machines and etc, and you could see this as a process of "decoding" (stretching the information processing metaphor too far, imho). but nothing was ever "encoded" there.

DNA comes to be the way it not by some kind of encoding process (it would if evolution were more like the Lamarckian idea), but by random mutation and natural selection, and is selected for the fact that, when it runs through that machinery, useful stuff is produced that supports the creation of more of that same DNA.

Since you get half of your genes from each parent, getting the specific let's say ALIGNMENT of the expression of genes is why your nose looks the same.

Cutaneous leishmaniasis will generally resolve without treatment in healthy individuals. Treatment of cutaneous ulcers in healthy patients is primarily preventing scarring. Most healthy people exposed to parasite species that cause visceral leishmaniasis don't develop symptoms, although more disease is seen in children and the elderly.

A lot of the answers here are long. The tl;dr is that DNA doesn’t encode information like “put the jugular at this position in the neck,” it encodes a bunch of molecular machines that together represent instructions that are more like “if you are an endothelial cell, contribute to vein construction when you encounter the hormone VEGF-A.”

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This! Virus infection is way more dangerous than a protozoa one, for example. The life cycle of a virus evolves basically entirely around infect host cells to reproduce. Protozoas are more complex, they have more particular needs to set the proper environment to reproduce successfully and also to transmite.

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Lovely and succinct answer. Thanks.

Space can be somewhat inferred by cells through hormone and signaling molecule gradients. So if a central group of cells can start releasing some sort of signaling molecule, and as cells get more distant from that central packet of cells they get less of that molecule, changing their behavior (ie gene expression).

Cells can also divide non-symmetrically, where one cell stays as one type and the other differentiates into a new cell type, creating shape. Cells can pass on information on what genes to express through chemical marks left on the DNA (and the proteins bound to the DNA) telling the new cell what genes to express and what genes to repress.

In the end, though everything does come back to gene expression, which is regulated by a complex network of gene expression networks generated by where the cell originated and what signals it is getting from where it is in the organism.

Interesting the actual genome in the nucleus does have a conserved 3D shape, which has a big impact on how it regulates its genome.