Biology
In: Biology
Genetic deseases are usually caused by an incorrected (mutated) peice of the dna. Children get half their dna from their mum and the other half from their dad. If a parent has a genetic desease there is a chance that their kid will get the broken bit of dna from the effected parent, which leads them to get the desease.
Genetic diseases are normally divided into two types those are recessive and dominant genes, those in recessive genes require both parents to be carrying the defective gene, otherwise the healthy gene from one parent overrides the unhealthy gene from the other parent. This type of gene can mean there are a lot of carriers of the recessive gene in the population without knowing it. The dominant gene means that the parent will have the condition and is far more likely to pass it on to the child, due to the disadvantages with having the gene these tend to be rarer. https://youtu.be/GTqXdraHe3E
For some genetic diseases, notably sickle cell anemia and cystic fibrosis, a single copy of the gene is protective. The sickle cell gene protects against malaria, cystic fibrosis against cholera. In populations at risk from those diseases, those genes strike a balance in the population between how many people are better off due to having a single copy of the gene versus how many are harmed by having both copies.
So that’s why. Kids get those diseases because they’re unfortunate enough to have two carrier parents with the modified gene, AND to have inherited that version of the gene from both parents.
Malaria is so nasty that there are at least two other genetic diseases that protect against it, favism and thalassemia.
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