Why does incest result in birth defects?

Comments

• Deestan@lemmy.world ⁨8⁩ ⁨months⁩ ago

  Human genes only really “work” when they are combined from very different sets.

  So-called “recessive” genes are overruled by your partner’s different pile of genes. They are usually shit traits like soggy bones or hair growing backwards, but since they never dominate, they haven’t been naturally selected away. They’re just harmless baggage.

  You can still get them because it’s all random, but the likelihood is generally low.

  If you don’t have that difference in mating genes, more of these recessive genes get to have a say in building the human. This severely increases the likelihood of birth defects.

  en.wikipedia.org/wiki/Inbreeding

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  • DharmaCurious@startrek.website ⁨8⁩ ⁨months⁩ ago

    It’s 4 in the morning and I’m sick, got them albuterol inhaler shakes, and “soggy bones” made me laugh so hard I went into a coughing fit.

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    • sangriaferret@sh.itjust.works ⁨8⁩ ⁨months⁩ ago

      It was backwards hair that did it for me.

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  • neuropean@kbin.social ⁨8⁩ ⁨months⁩ ago

    For mars, they could do whole-genome sequencing and select for people with fewest deviations from the de facto wild-type human genome.

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    • ilinamorato@lemmy.world ⁨8⁩ ⁨months⁩ ago

      That sounds unsettlingly like eugenics.

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• HobbitFoot@thelemmy.club ⁨8⁩ ⁨months⁩ ago

  Genes mutate.

  If you have one copy of a mutated gene, it could be bad. However, one mutated gene is usually recessive or will be co-dominant with the other gene so it isn’t that bad. If you have two copies of that gene, it can be a lot worse.

  Two close family members are more likely to have the same mutated gene, so the odds of getting that same mutated gene twice are a lot higher.

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• sosodev@lemmy.world ⁨8⁩ ⁨months⁩ ago

  Many families have recessive fucked alleles that cause all kinds of problems. An allele is a variant of a gene. You need two copies of a recessive allele for that gene to be expressed (do something).

  Every fucked allele the parents share has a 25% chance of being expressed in the child. The more DNA the parents share the more fucked alleles they share. Usually… sometimes the opposite happens and the number of bad alleles is reduced in the child. Inbreeding can lead to fucked animals and “perfect” ones. Weird stuff.

  Now you might be thinking “why do families have so many fucked alleles?”

  That’s a good question. The thing about carrying a single recessive, fucked allele is that it doesn’t do anything to you. Mutations happen all the time and so these alleles are floating around and multiplying constantly.

  It’s only a problem on the odd chance that they get expressed which is most often when family members produce offspring.

  So it’s worth noting that this is the type of thing that we can check for these days. In some cultures it’s acceptable to marry a cousin and I’ve heard that they check for any genetic issues before proceeding when they live in a first world country.

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