Biology 1201A Lecture Notes - Lecture 8: Sickle-Cell Disease, Red Blood Cell, Heterozygote Advantage
24 May 2016
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Heterozygote advantage: selection in which the heterozygous phenotype has the highest fitness. In order for heterozygote to have the highest fitness, the inheritance pattern must be incomplete dominance or codominance. The phenotype for the heterozygote must be unique and distinguishable from the homozygous phenotype. People with sickle cell disease cannot carry oxygen as efficiently, therefor their fitness is lower: in heterozygotes, some red blood cells function properly, but some don"t. To answer the question we used simutext simulations. Refer to graph below for results of simulation. Homozygous r individuals are being killed faster than ss induvial, which is pushing down the r allele frequency. Because the fitness of rr is so low, they are not generating a lot of r alleles for the population to produce a heterozygote. Even though we have heterozygote advantage, the selection against rr is so strong that we don"t get a lot of.
