Like when a baby is born and has a randim mutation
In: Biology
When the code inside your cells gets damaged enough it cannot order to destroy itself so it keeps reproducing the same mistaken pattern
Defects in the DNA across parents. So a part of your DNA might be confused for another part of your mommies DNA, causing something different!
The process your cells use to multiply themselves isn’t perfect, and they make mistakes copying your DNA.
When cells split, they have the copy the DNA. They unspool it, split it apart from DNA into two RNA strands, and then take raw material to fill in the gaps and turn both RNA back into full DNA. The tools used to do this are different kinds of enzymes.
Mistakes happen at various points in that process. A single amino acid can be replaced with a different one. A whole section can get repeated or cut.
Then there’s radiation. The amino acids and structure of your DNA can be literally and directly broken with a blast of radiation. Which is what most of what a sunburn is, and why we make a new layer of skin so fast. Some radiation doesn’t lead to mutant kids, it all gets absorbed by the skin. Some radiation goes right through without bothering anything. The stuff in between goes through and messes up stuff all along the way. We use UV light to scramble bacteria’s DNA. It doesn’t actually kill it, but the next generation is non-viable.
You body has a lot of ways of dealing with that. If a cell’s code doesn’t work, and just seg faults or whatnot, then it’ll die or be killed off and they’ll try again. (Or it’ll break it’s programming and become cancerous). But egg and sperm cells are more fragile without (as many) ways of dealing with damage. When kids are made with damaged DNA, they don’t have any good copies. One tool we do have is two sets of DNA data, if one gets messed up with radiation, we switch to the backup copy chromosome.
You know how sometimes when you make a photocopy of something, theres a string on the glass, or the corner gets bent out of shape, and you dont notice it until after the copy is done? Its the biological equivalent of that.
As far as at a fundamental level, the A-T and G-C bonding is strong and specific, but it’s not as strong as a covalent bond. And there are no strong repulsive forces between mismatched nucleotides so it would be expected for a few errors among every base pair in the genome. Gene editing systems evolved to correct these random mismatches as genome size increased, but between the trllions of enzymes carrying out the gene editing process, mistakes are going to happen. I would be fascinated to see if these systems have evolved not to be too efficient, logically a very small percentage of random mutation is more evolutionarily fit than no mutation at all.
Here’s an easier analogy I read a while back:
Try to take a novel and a pen and paper, then try to copy down the entire novel handwritten.
You’re almost positively going to make some mistakes. Same with your body copying DNA.
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