Eli5: What are recessive genes? Why do we always get passed down genes that don’t show?
In: 5
In the most basic form, you get 2 versions of each gene called alleles. one from each parent. some of the alleles are recessive, meaning you need one from each parent for it to show, some are dominant which means you only need one.
take eye colour for example. the allele for brown eyes is dominant while the one for blue eyes is recessive. If someone has 2 brown eye alleles, they will have brown eyes, if they have 2 blue eye alleles they will have blue eyes, but if they have one of both, they will have brown eyes as brown is dominant. If you have a recessive allele but don’t show it, your called a “carrier” of that gene.
when you have kids, you only pass on one of these alleles. if someone with 2 brown alleles has a kid with someone with 2 blue alleles, the kid will always get one of both and have brown eyes.
however if 2 people with one brown and one blue allele have a kid, theres a 25% chance the kid will get have 2 brown, 50% chance they’ll have one brown, one blue, and a 25% chance they’ll get 2 blue snd have blue eyes. This means 2 people with brown eyes can have a kid with blue eyes if they both had the recessive gene.
This example was with eye colour, but it also goes for genetic diseases. Even if you, and your partner don’t have any genetic diseases, you can still pass them on to yours kids if you were both carriers
edit to say im not an expert, this is just what i remember from school
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