Eli5 what decides whether genes are dominant or recessive

Question

Eli5 what decides whether genes are dominant or recessive

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Answer 1

As a rough generalisation dominant genes are because they produce something that causes an effect whereas recessive genes are genes that fail to produce something.

So eg Albinism (lack of melanin) is recessive because if you only had one copy of the gene causing albinism then your other normal gene could still make melanin.

Whereas dominant huntingdons diesease is because the mutated form of the gene basically makes a toxic protein. So even if you had one normal copy the mutayed foem would still be affecting you.