6 ms·

FWIW, your last paragraph is a little misleading. I think a better way to state it is that you can be 100% certain of selecting embryos that do not have disease

FWIW, your last paragraph is a little misleading. I think a better way to state it is that you can be 100% certain of selecting embryos that do not have diseases caused by specific, known single genes. Selection can still be extremely effective on polygenic traits (traits influenced by a huge number of different genes), it's just that there isn't a single switch that you're turning on or off. After all, you're selecting the most intelligent (or, more specifically, the most likely to be the most intelligent) out of several dozen embryos. That is like artificial selection on steroids. And I should add: in theory. Right now we still don't know all the various genes that are responsible for intelligence and, as I understand it, there's a good chance that a significant number of the genes involved in a polygenic trait like intelligence are what are called rare variants. IE, they're not widely present in the population and are instead specific to certain lineages. If that's the case, then it will be hard to identify those and select the ones present in you and your mate's respective lineages.

pjscott 7y ago
The article I linked put it way better than I did, so I'll just quote that for clarification: > One of the key problems is that polygenic scores are the sum of many individual small genes’ effects and form a normal distribution, which is tightly distributed around a mean; the further into the tail one goes, the larger a sample it requires to realize a gain—to put it another way, if you have 10 samples, it’s easy (a 1 in 10 probability) that your next random sample will be the largest sample yet, but if you have 100 samples, now the probability of an improvement is the much harder 1 in 100, and if you have 1000, it’s only 1 in 1000, and worse, if you luck out and there’s an improvement, the improvement is ever tinier.
jakobegger 7y ago
> That is like artificial selection on steroids No, it's not, because you are selecting on genotype rather than phenotype. Embryo selection only works when there is a simple connection between genotype and phenotype (eg. what type of earlobes do you prefer). For complex traits like "intelligence", selecting based on genotype is not going to work. To much noise, too little signal.
- sanxiyn 7y ago
  Note that we are already doing genotype selection on dairy cattles using "net merit", a proxy for lifetime profit, and succeeding. That's pretty complex too.
- haihaibye 7y ago
  Polygenic risk scores are the distillation of the signal, achieved by enormous sample sizes. They work. Fisher showed in 1918 you can perform selection even if there were an infinite number of loci involved, see https://en.m.wikipedia.org/wiki/Infinitesimal_model https://en.m.wikipedia.org/wiki/Infinitesimal_model

pjscott 7y ago

The article I linked put it way better than I did, so I'll just quote that for clarification: > One of the key problems is that polygenic scores are the sum of many individual small genes’ effects and form a normal distribution, which is tightly distributed around a mean; the further into the tail one goes, the larger a sample it requires to realize a gain—to put it another way, if you have 10 samples, it’s easy (a 1 in 10 probability) that your next random sample will be the largest sample yet, but if you have 100 samples, now the probability of an improvement is the much harder 1 in 100, and if you have 1000, it’s only 1 in 1000, and worse, if you luck out and there’s an improvement, the improvement is ever tinier.

jakobegger 7y ago

> That is like artificial selection on steroids No, it's not, because you are selecting on genotype rather than phenotype. Embryo selection only works when there is a simple connection between genotype and phenotype (eg. what type of earlobes do you prefer). For complex traits like "intelligence", selecting based on genotype is not going to work. To much noise, too little signal.

sanxiyn 7y ago
Note that we are already doing genotype selection on dairy cattles using "net merit", a proxy for lifetime profit, and succeeding. That's pretty complex too.
haihaibye 7y ago
Polygenic risk scores are the distillation of the signal, achieved by enormous sample sizes. They work. Fisher showed in 1918 you can perform selection even if there were an infinite number of loci involved, see https://en.m.wikipedia.org/wiki/Infinitesimal_model https://en.m.wikipedia.org/wiki/Infinitesimal_model