https://www.reddit.com/r/askscience/comments/w4bi3e/what_makes_one_feature_dominant_and_other/
created by Gloomy_Efficiency196 on 21/07/2022 at 08:42 UTC
46 upvotes, 4 top-level comments (showing 4)
I want to know why some features in genetics are dominant and can overcome this recessive ones, how they do this, what is the difference between them?
Comment by [deleted] at 21/07/2022 at 10:36 UTC
45 upvotes, 2 direct replies
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Comment by [deleted] at 21/07/2022 at 22:04 UTC*
4 upvotes, 0 direct replies
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.
Comment by [deleted] at 21/07/2022 at 11:51 UTC
1 upvotes, 0 direct replies
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Comment by swat_08 at 27/07/2022 at 16:27 UTC
1 upvotes, 0 direct replies
Here is another insight, consider this picture[1] , this is an example of the phenomenon of incomplete dominance. In incomplete dominance whenever a locus contains 2 types of alleles that are heterozygous i.e. nonsimilar (Rr) the flower color results in pink in color but when all the dominant alleles (RR) are present at that locus the flower color results in deep red, similarly when recessive alleles are present the flower color results to white. This happens due to the different combinations of dominant and recessive alleles when they are present at the same locus.
1: https://www.toppr.com/ask/en-mv/question/whatis-incomplete-dominance-write-its-example/
One other example is Complementary genes picture[2] when a dihybrid locus contains two dominant genes (CcPp, CCpP, CCPP, CcPP) then only certain flower color would be expressed or another phenomenon, but when the two dominant genes aren't expressed together(Ccpp, CCpp, ccPP, ccPp, ccpp) then that flower colur would be changed onto some different color.
2: https://www.majordifferences.com/2019/01/difference-between-complementary-genes.html