This is going to be a very niche item. That said, the more of you lace makers I meet, the more I grasp the heavy sci-tech nature of this couvige. 

https://www.nature.com/articles/s41467-022-33366-x

High-resolution silkworm pan-genome provides genetic insights into artificial selection and ecological adaptation

Anyway: researchers sequenced the DNA of silkworms. They picked different silkworms around the world to compare them. In some species, they might still have a gene that another variety lost. Or some have a gene turned up to 11 that's only set to level 3 in another one. 

They found that one crucial different between fine and coarse silk, in this gene:

We found an 11.1 kb intron insertion and a 6.2 kb downstream insertion of the chitooligosaccharidolytic beta-N-acetylglucosaminidase (BmChit β-GlcNAcase) gene in Chunfeng and Suxiu strains (Fig. 6f). We found that the BmChit β-GlcNAcase gene is expressed at a significantly higher level in fine silk strains (Suxiu, Chunfeng) and has an expression peak in silk press at the wandering stage (which occurs at the start of spinning) (Supplementary Fig. 6b, c). CRISPR-cas9 mediated knockout of the BmChit β-GlcNAcase gene produced coarser silk (Fig. 6g, Supplementary Fig. 6d). All these results suggest a key role of the BmChit β-GlcNAcase gene in the determination of silk fineness.

I don't understand what that gene does yet (but it sounds to me like it cuts sugars off, which makes sense...), but it looks like the key. So this gene, when turned up, makes silk finer. When they knock it out, it's coarser silk.

This is wicked cool.