GENOTYPES & PHENOTYPES


For me while growing up, genotypes simply meant whether or not I carried the sickle cell gene and how to avoid marrying a partner who did. The term phenotype was a foreign one I had never heard of until researching information for this post today.

Both terms were coined by Danish scientist Wilhelm Johannsen in 1911 and he defined a person's genotype as the genetic makeup of their hereditary identity that is used usually when talking about the genetics of a particular trait. The phenotype is the observable physical or biochemical characteristics of an individual by both their genetic makeup and environmental influences. In other words, the genotype is the set of genes in our DNA responsible for a particular trait while the phenotype is the physical expression or characteristics of that trait.

There are a total of 6 different genotypes: AA, AO, BB, BO, AB & OO and when discussed in relation to sickle cell, genotypes and phenotypes help you and I understand their significance. Human beigns are diploid organisms by nature ( meaning they have 2 alleles) that inherit one allele from each parent and this in turn is what makes up their genotype. An 'allele' is one of 2 or more variant/alternative forms of a gene that arise by mutation and are formed at the same place on a chromosome. Note that different alleles can result in different observeable phenotypic traits.

Individuals with genotype AS have the SC trait phenotype and those with SS genotype have the SC disease phenotype. Terms like 'dominant', 'recessive', and 'co-dominant' do not actually describe the gene but the trait and this means that the same variant(or allele) of a gene can be dominant, recessive or even co-dominant. Confusing stuff eh? trust me, I was scratching my head as well but the general gist is this:
- if for example, one of your red blood cells is the sickle shaped cell, then you are resistant to malaria. The sickle cell allele is co-dominant while in terms of resistance to malaria, it is dominant but in terms of sickle cell anemia, it is recessive. In summary, one allele can have 3 different dominances and so we focus on the trait (phenotype) of the gene and not on the gene(genotype) itself.

Different genotypes can make a single phenotype and one genotype can make different phenotypes. Understanding how a trait is made will therefore mean thinking about what the alleles do in that specific case. There is a more in-depth analysis of these terms that I think is worthy of checking out here to help you understand the above analysis a little better.

I am personally still researching this topic so I can relate it to myself and siblings to see what traits we have/exhibit because of our genes. I think it would be interesting to see and I am kinda curious too so if you have some time, check out the article and then you can brag to your family about knowing some 'science' stuff, LOL!

So glad I can learn and share with you my findings and my experiences with sickle cell. Can you identify the traits you have and relate them to your genotype? I'm figuring mine out as we speak...

Always Love 💖


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