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The Science Research Manuscripts of S. Sunkavally, p 811.

Phenotype vs Genotype

Phenotype -- the trait produced by the genotype -- depends on both genotype and environmental factors -- not inherited by offspring -- consists of expressed genes -- dominant alleles can mask recessive alleles -- genotype AA causes phenotype A -- genotype Aa causes phenptype A -- genotype aa causes phenotype a

Genotype -- the actual genetic code of an organism -- codes for the phenotype -- consists of both dominant and recessive alleles -- inherited by offspring -- usually refers to one specific gene causing a trait -- written as a combination of uppercase and lowercase letters -> AA -> Bb -> ee -- dominant = uppercase letters -- recessive = lowercase letters -- both uppercase = homozygous dominant -- one uppercase and one lowercase = heterozygous -- both lowercase = homozygous recessive

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So I'm working on a dystopian-esque story in which spouses are assigned by the government based on matches that would produce ideal offspring. The idea is to "perfect" humanity, and use this process to ereadicat disease. What are somethings that might go wrong with this as far as genetic mutations go or in general? Also, can you recommend a few research sources? What testing would be needed to determine matches? I need all the help I can get! Thanks so much!

Hi there!

There are a few questions you have going on here, and I’m going to answer them in order of shortest to longest answer, and in a way that lets them build on each other. At the end, I’ll include some extra resources and reading you could do to help round out what I’ve said here.

The testing could be done in a couple of different ways- either you could sequence every single person in the population, or you could genotype them, using a functional set of specific markers. I’m going to guess that if the government in your story is going through the effort of basically implementing a mandatory, population wide eugenics program, they are probably going to go for the “sequence” option. It’s the more expensive and in-depth of the two, but is also going to give you full-genome wide information, rather than just looking at a selected subset. The disadvantage of sequencing is that you are going to get EVERYTHING, which can be more information than you need or are looking for. Genotyping can be set up to only look at the functional parts, rather than all of the non-coding parts of the DNA.

So we’ve sequenced everyone, and now we know about all of their genetics, so the next step is pairing everyone up. You said that the primary goal is to eradicate disease, which you could do a certain extent with genetics, but not all the way. You would be able to select matches that would prevent hereditary diseases in your population, but that won’t stop people from getting the common cold! There are very few genetic diseases that are dominant traits, which helps us out here. What you would be able to do is match carriers of these diseases with non-carriers, and that would take away the possibility of their children having that disease (although the children may still be carriers themselves). The next step that could be taken once you have pools of people that can be matched is try and introduce as much heterozygosity, or hybrid vigour, into your population as possible. Genetic variability is your friend, and ensuring that the population crosses are as different as possible means that the children of those populations will be more fit for any environment, and also ensure that they create continuously unique populations. Generally speaking, in the world of genetics, having a very flat population with few differences is bad, because it means if the environment changes, there is no variable group that can deal with that change. Different is good!

So how could this all go horribly wrong? Well, mutagenesis is a strong influencer in genetics. Spontaneous mutations crop up from normal DNA replication and environmental influences regularly. As a general rule, they aren’t harmful- that’s part of the reason we have so much non-coding DNA. If something happens in those regions it’s much less likely to have a negative effect than a mutation in a coding region. But, things happen, and sometimes a mutation occurs in a coding region, leading to a new trait/disease.

For your recommended reading, I would look into both the Wikipedia articles on “heterozygote advantage” and “loss of heterozygosity”. I think they give a good overview of why you want genetically diverse populations.

Here is a link to one of my favourite studies where they had women smell the body odour of different men and rate their preferences. What they found is the women preferred men who were heterozygous on three MHC loci, which has been related to enhancing the rate of disease resistance. It’s an interesting study, and I think relevant to your story. https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1689917/pdf/10380676.pdf

I hope this helps, and if you want more info on any part of this, just send me another ask!

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