Why does same family mating develop mutated offspring?
In: Biology
Genes have two copies, and one of them from each parent is randomly picked to go to the offspring. One gene is dominant and the other is recessive; the dominant gene always overrides the recessive gene.
If one of the genes mutates into something bad, it’s usually rarer and overpowered by the stronger, normal gene, and doesn’t do anything.
If a parent has one bad copy, it has about a half chance to be part of the child, and the same with the other parent; if two bad recessive genes wind up in the child, they do something bad.
Because having one bad gene doesn’t cause problems (and can even be good sometimes), lots of people have the mutations and pass them down. This means you and your relatives could very well have inherited bad genes from your ancestors. If you and some relative both have one bad gene when you screw, there’s a one-in-four chance the child will have the active mutation. And there are a lot of genes.
It doesn’t really cause mutations. What it does do is increase the chance for existing mutations in the parents to be reinforced in the offspring. Every person (or sexually-reproducing organism) receives one set of genes from their mother and another redundant set from their father. Many potentially harmful mutations are harmless if the organism also has a good copy of the same gene.
So, if the mother and father are related, there is a chance to get two copies of a bad gene. This is less likely if the parents were unrelated.
Genetic defects are minimized through diversity, since most are recessive genes and suppressed by dominant genes. But, if two family members have the same recessive gene, the chances of it being expressed (giving the kid problems) go way up.
Basically, everyone has the chance to develop defects. But two people with the chance for the same one makes for a much higher chance.
You get genes from both parents.
If one of those genes is bad, the good one will usually be dominant.
This means you won’t suffer any effects from the bad gene, but you have a chance of passing on that bad gene to your children.
If you have a child with a stranger, it’s unlikely you have the same bad genes. That means you have a relatively small chance of your children having genetic defects.
If you have a child with your sister, there is a good chance they have the same bad genes as you and you are much more likely to pass on those defective genes.
This isn’t too bad in one generation. The chance of passing on bad genes is still low, but it gets much worse if future generations keep having children with relatives.
The chance of both parents having the same defective genes gets higher each generation.
That’s how you get a whole line of royals with hemophilia.
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