Why are dominant genes dominant

And recessive genes recessive?

Because you touch yourself at night.

Because that's just how it works? There's nothing that makes a allele recessive or dominant, it's just how they interact with others in the same gene.

Consider the case where someone is homozygous for some trait. Both alleles code for the same enzyme, which causes a trait. Only a small amount of that enzyme may be necessary for a given phenotype. The individual therefore has a surplus of the necessary enzyme. Let's call this case "normal". Individuals without any functional copies cannot produce the enzyme at all, and their phenotype reflects that. Consider a heterozygous individual. Since only a small amount of the normal enzyme is needed, there is still enough enzyme to show the phenotype. This is why some alleles are dominant over others.

As many genes code for enzymes, I'll use them as an example. Consider if someone is homozygous for some random trait. Both alleles code for the same enzyme, which causes a trait. Only a small amount of that enzyme may be necessary for a given phenotype. The individual therefore has a surplus of the necessary enzyme. Let's call this case "normal".

Individuals without any functional copies cannot produce the enzyme at all, and their phenotype reflects that. Consider a heterozygous individual. Since only a small amount of the normal enzyme is needed, there is still enough enzyme to show the phenotype.

This is why some alleles are dominant over others, hope that helped. http://en.wikipedia.org/wiki/Recessive_gene#Mechanisms_of_dominance = further reading.

lol copypasta

>>4

why did you post one version with the sentences all concatenated, and then another with them broken up? 'the fuck?

Because God made them that way.

>>4
Nice copypasta.

But that's a pretty poor explanation. All that shows is that a knockout on only one chromosome will often still be functional. It doesn't explain anything about dominance. If that were the only explanation, all genes would be codominant.

Dominance is something that would have to be looked at on a gene by gene basis. Each case is a matter of how the alleles interact, and can't be generalized easily.

>>8
But then shouldnt they teach a myriad of fragmentary reasons for specific dominances on the aforementioned gene by gene basis rather than generalizing?

>>9
Who's teaching generalizations? I was never taught 'why' dominance exists, simply that it does. Why's that? Because there's no use teaching what you don't know.

>>10
By what was said, "dominance" doesnt exist, only a myriad of allele interactions that combine into a web of madness that we currently refer to only as "DOMINANCE"

They aren't. Recessive genes have an effect on the effect of the gene, it is just not as pronounced. Someone with a recessive gene that allows immunity to a disease and a dominant gene that does not allow immunity will have a reduced immunity to the disease rather than a complete absence.

>>12
Not always. That's incomplete dominance. Many cases a heterozygote is phenotypically indistinguishable from a homozygote. Take Mendel's peas, the gene for flower color, white vs purple or whatever. The heterotygotes have exactly the same pigmentation as the homozygotes. The functional allele produces more than enough enzyme, while the non-functional allele simply does nothing. At a molecular level you might have inactive enzyme floating around, or you might notice there's a bit less enzyme than you expect, but at a phenotypic level, they're identical.

>>11
this clarification of why we call it what we do isn't an explanation of why it does what it does.