The statement “dominant alleles may have a novel function”
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I’m not sure, but I guess you asked to explain what that statement means?
If that so, then first what is allele – it is a variant of some gene. Each people have unique set of DNA, but if we get DNA of entire humanity and average it using only most frequent DNA letters, we get a typical genome. Almost all people would have same genes, but many people would have some variation of them – here or there one or few letters would be different. That’s alleles.
Now, what is a dominant and recessive alleles. Some (and I emphasize – only some) mutations switch some genes off, and that would be a recessive allele, it’s either doesn’t get read by proteins or it’s proteins doesn’t fold like they should, or something else. Anyway, that gene is essentially doesn’t work like it should.
Because humans (and any animals and plants) have two sets of mostly identical chromosomes, same gene could (and usually does) have a two different alleles (i.e. two copies with some random variations) in one person. So, if one allele is recessive, i.e. it doesn’t work, there’s a high chance that another one in second set of chromosomes does work, therefore a function, which is encoded by such gene, still works.
Finally, some mutations could change gene in such a way that resulting proteins could end up having different shape. They could be not working as usual proteins of this gene, but still be produced by cellular mechanisms, and with further mutations they could end up with quite different protein with different function, or be removed by selection. And if they do end up with different function – that’s a novel function.
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