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View submission: What makes one feature dominant and other recessive?
Other answer is great. Just to provide a little extra information, most traits are not Mendelian IE not directly determined by dominant and recessive genes. Most traits are actually determined by lots of different genes working together.
As the other answer illustrates, it’s all about what protein a gene makes. Sickle cell is a good teaching example. Black people have sickle cell at a higher rate because it provides protection against malaria, and most American Black people are from West Africa where malaria is prevalent.
Sickle cell is caused by a mutation in a gene that makes part of a blood cell. You have two copies of every gene. People with two “normal” hemoglobin genes are susceptible to malaria, but have healthy blood. People with two sickle-cell hemoglobin genes are protected against malaria but suffer from sickle cell disease. People with one normal gene & one sickle cell gene have the best of both worlds; protection from malaria AND relatively healthy blood. Both genes make proteins, so if you looked at a person with both genes’ blood, you’d see some sickled cells & some normal round cells. You could call the sickle cell gene “recessive” but it’s not classically recessive.
A lot of recessive traits still do create some change if they’re present alongside a dominant copy; that change is just usually small, as whatever function is affected is predominantly affected by the dominant gene. In the above case the fact that there’s still some normal blood cells means that sickle-cell disease is not present as long as one copy of the normal gene is present. Therefore sickle-cell disease is a recessive trait.
A person with the two different genes is called a heterozygote and sickle cell is prevalent because heterozygotes do better in their environment; this is called “heterozygote advantage”. That’s probably getting away from the question but I find it cool & feel like mentioning it.
Maybe this is too much information, but I wanted to provide a little more for those curious. I have done some biology teaching & find that a lot of people think that everything is dominant and recessive. I also find that a lot of people are, like you, not sure what makes dominant and recessive traits work. I hope the above info adds on to the other excellent answer.
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