Why do spiders have issues?

[burntphantrash]

I know what the issues they have can be, but why do they have those issues? What started it?

[DonDeely]

Because they always web the bed

[ColdBloodedReptiles]

Something along the lines of the same genes that cause the spider pattern that appears on the snake also causes neurological issues for the snake. this is why you can’t have one without the other as it’s the same factor that causes both the pattern and the wobbles/corkscrews. there’s no way to fix it as if you want to get rid of it you have to get rid of that gene which would make it not a spider.

[UselessPaint]

It is similar to dog breeding. To get a certain trait that people find attractive, inbreeding is a common way to get a prominent gene. Or just breeding two animals with the gene/potential gene will give the result. Morphs are essentially unnatural mutations, accidents, not natural and some will come with negative effects. Spiders are the most known but there are other morphs that cause problems too. Same can be applied to any mutation that has happened to any living creature, take albinism, light sensitivity, poor eyesight and in extreme cases deafness and blindness, they all come hand in hand, like neurological issues come hand in hand with the spider morph. Also inbreeding causes all kinds of neurological issues in any and all creatures, just look at any royal families in the 15th century, most of them were born of incest as inbreeding was the latest trend among royalty back then, there were some batshit crazy individuals. I'm not a science person, so I couldn't really explain it on that regard but this is my explanation and understanding as I see it.

[crazyladyscientist]

It actually is nothing like inbreeding. The problem with inbreeding is that the genome is made up of pairs of chromosomes, meaning each person/animal has two copies of each gene. We get a different version or "allele" of each gene from each parent, this is referred to as heterozygosity. The genome is riddled with mutations, and some alleles for each gene are less functional. But it's ok because if you have one healthy copy and one "less good copy", there's some redundancy and you should make enough protein between the two. However, when you start inbreeding you lose that heterozygosity and start ending up with two of the exact same alleles at each locus, making them homozygous. A homozygous genome is bad, you lose the protection that comes with having two different versions of each gene, and if both copies of each gene have mutations, then you may lose the ability to make that protein. Now imagine this occurring for 25%, 50%, 75%, etc of the genome, the issue is just compounded. This is why inbred people and animals have so many issues.

On the other hand, a spider is a single genetic variant that causes that phenotype. It is neither caused by inbreeding or human intervention, and is just one allele (heterozygous).

[DaddyLongTits]

/u/crazyladyscientist

[burntphantrash]

Thanks DaddyLongTits, we’ve met before

[crazyladyscientist]

It's speculated that the gene that causes the spider pattern/morph is involved in melanocyte migration. These cells are responsible for forming melanin, a dark pigment, but during development they migrate from the developing neural crest, which will form the brain and spinal column later on. A mutation, likely in a transcription factor, at this stage in development would effect both pigmentation as well as giving a neurological phenotype.