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Is that a yes?

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It's not genes that are recessive or dominant, it's variants (alleles) of genes. A recessive allele is generally a gene that doesn't work, but if your other copy of the gene still works you still have enough activity to be unaffected. Changing that to a dominant allele isn't trivial. I can't come up with any examples of that happening quickly in evolutionary terms. On longer timescales it's easier, like if the gene product goes from acting as a monomer to a dimer and the broken allele then makes the dimer inactive - then the loss of activity can be enough to leave heterozygous individual affected.

I think, they are relative to each other. Like, dark eye color is dominant. Other gene might have been expressing its own color too, but the dark color is what we see effectively at the end.

Different genes may have different mechanisms, but the idea is how a single gene can't be enough for making that function effective.

For example, we might have three eye colors which, one is dominant to other, and the last one is recessive to both. Like, A > B > C or something. If gene A somehow would get disappear from the genetic pool, then we might start calling B simply a dominant gene, instead of comparing it with another.

This is wrong. Some genes can be recessive but not affect the person if the other gene is able to meet the functioning threshold (like make enough of some enzyme), however at times just one recessive gene is enough to cause a disease or other phenotype problem (think a gene that produces a mutant protein that your body can't get rid of). Thats why there are heterozygous diseases

In short, yes. The quickest ways would be via a bottleneck or founder effect, like Pingelap Atoll where a largw portion of the population has a recessive form of colorblindness. But in a normal population with genetic drift and flow, this is pretty unlikely to happen

> however at times just one recessive gene is enough to cause a disease or other phenotype problem (think a gene that produces a mutant protein that your body can't get rid of).

That's not a recessive gene. Firstly, it's not genes that are recessive, it's alleles. Secondly, what you're talking about there is a dominant allele.

That isn't turning a recessive allele into a dominant allele. That's turning a rare allele into a common allele.

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Alleles are variants of genes. And no, still talking about recessive. Sickle cell, as an example, is a recessive disease and is still expressed in heterozygotes

recessive alleles are in general rare. If you got a group of recessive homozygotes and some heterozygotes and put them on an island where there is no genetic flow or drift then you get a population where that recessive allele is widespread

So first of all, it's not genes which are dominant or recessive, it's alleles. Alleles are variants of genes. For example, there's a blood type gene with alleles A, B, and O. You generally have two alleles of each gene, since you have two copies of (most) genes.

Alleles are dominant or recessive as a side effect of how they work. For example, consider a gene that's involved in melanin production. It's got an allele that makes melanin normally. And it's got an allele with a mutation that makes it not work. A cell will activate this gene if it senses the cell doesn't have enough melanin.

If you have two copies of the working allele, you get melanin. If you have one copy of the working allele and one of the busted allele, you get melanin. If you have two copies of the busted allele, you get no melanin. So the working allele is dominant.

Now, to get back to your question, can this change? Well...no. Because if an allele changes, it becomes a different allele. An allele is a specific version of a gene. If you mutate it in some way, you make a new version of that gene, a different allele.

Dominance and recessiveness aren't even absolute things, they depend on which other allele you are comparing to. For example, go back to A B O blood types. A is dominant over O, but it's not dominant over B. If you have A and O alleles, you just have type A blood. If you have A and B alleles, you have AB type blood. So is A dominant, or not?

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Well no. Full-blown sickle cell disease only affects homozygotes, and as such is considered recessive. But the heterozygotes do still have a different phenotype than either homozygote in some ways. That means in those respects the allele is not recessive at all. When it comes to malaria resistance, it's more of a dominant allele.

Idk what mental gymnastics you going through to term a recessive disease "dominant". Sickle cell heterozygotes are just in between full blown sickle cell and normal, thats just codominant expression but the disease is still recessive because if it was dominant then heterozygotes would have full sickle cell. Need to inform yourself before making bogus claims online

https://medlineplus.gov/genetics/condition/sickle-cell-disease#:~:text=Inheritance&text=This%20condition%20is%20inherited%20in,and%20symptoms%20of%20the%20condition.

Read your own source:

>This condition is inherited in an autosomal recessive pattern, which means both copies of the gene in each cell have mutations.

Your source does explain that it gets complicated when there are, for example, two different kinds of mutations in the two copies of the gene. That obviously goes beyond the simple categorization of recessive vs. dominant.

Other sources make the definition even clearer, like this:

>sickle cell anemia, which is defined as homozygosity for the sickle hemoglobin (HbS) gene (i.e., for a missense mutation [Glu6Val, rs334] in the β-globin gene [HBB])

i agree with the other comments on genes vs alleles and that it is often more complicated than recessive/dominant as in u/atomfullerene's example with blood types. but if i'm understanding what you meant, i think the question you were getting at is can a rare/generally considered detrimental allele become beneficial and widespread in a population.

if that's what you were asking, the answer is yes. and in terms of time, it would depend on how beneficial the allele is. an example is sickle cell anemia. Whilst it's normally a rare and detrimental mutation, it became pretty widespread in africa because it can be protective against malaria. In this situation the death from malaria was more frequent than the death from sickle cell, at least before the child-bearing ages, so this change was decently fast. here's a link if you're interested in reading more about this: https://sickle-cell.com/clinical/malaria

Hey i want to ask, if the person has 2 alleles , 1 positive with sickle cells another is a normal function allele.

So is the sickle cell allele still working and you make false proteins but with the another allele still works normally then you still can be alive because your blood now consist both false hemoglobins and normal hemoglobins ( and the normal hemoglobins is in sufficient amount for you to be alive ? ).

I thought at first if an allele is reccessive and another one dominant then the reccessive allele will be locked , only the dominant will be working or switch ON. So whats wrong can you please explain..

Thanks for you reply , very informative! And btw is the O allele is zero production of the antigen protein on the cell surface ?

Yep