substitution
See the attached link.
SS,Ss
Yes, the genotype SC refers to individuals who have inherited one sickle cell allele (S) and one C allele, resulting in a sickle cell trait that is different from having sickle cell disease. This genotype can lead to some symptoms similar to sickle cell disease under certain conditions.
It's not sickle-cell itself, but rather being a heterozygous carrier of the disease. People with one dominant and one recessive allele for the disease are immune to malaria without the crippling effects of having sickle-cell anemia. I don't think that it can even represent codominance, though.
Sickle cell disease is an example of codominance, not heterozygous dominance. In individuals who are heterozygous for the sickle cell allele, they exhibit a milder form of the disease called sickle cell trait, which demonstrates codominance of the normal and mutant hemoglobin alleles.
The absence of the selection pressure malaria. Without selection, in the form of the malarial environment, the sickle cell allele will be lost in the overall US population. Even the heterozygous condition is somewhat deleterious and, statistically without malarial selection pressure the allele will be selected out.
The pro of sickle cell hemoglobin is that if you have only one allele for sickle cell hemoglobin and the other allele is normal, then you are immune to malaria.
codominant
codominant
The allele for the sickle cell trait is codominant with the normal allele. This means that in individuals with both alleles present, both traits are expressed.
Since people with the sickle cell allele trait are resistent to malaria, if malaria were eliminated there would be no change in the frequncy of sickle cell allele. This is because the presense of malaria does not have an affect on patients with the sickle cell allele trait.
SS,Ss
The sickle cell allele can be maintained in the central African population, above the frequency of gene mutation (balancing selection), because the heterozygous sickle cell individuals have an advantage in lifespan, in this malaria stricken region, over the homozygous alternatives. Homozygous sickle-sickle individuals die early from the sickle cell disease. Homozygous nonsickle-nonsickle die early from malaria. The heterozygous sickle-nonsickle have a higher survival against malaria and therefore the sickle cell allele is balanced selected.
Yes, the genotype SC refers to individuals who have inherited one sickle cell allele (S) and one C allele, resulting in a sickle cell trait that is different from having sickle cell disease. This genotype can lead to some symptoms similar to sickle cell disease under certain conditions.
It's not sickle-cell itself, but rather being a heterozygous carrier of the disease. People with one dominant and one recessive allele for the disease are immune to malaria without the crippling effects of having sickle-cell anemia. I don't think that it can even represent codominance, though.
Around the mediterranean sea.
Around the Mediterranean Sea.
Around the Mediterranean Sea.