Sickle Cell Anemia Flashcards
Phenotypes and Genotypes and Survivability:
Normal Hemoglobin
Genotype: (HbA/HbA)
Phenotype: All red blood cells are normal.
Survivability:
Without malaria: High survivability.
With malaria: Higher risk of death due to susceptibility to malaria.
Phenotypes and Genotypes and Survivability:
Sickle Cell Trait
Genotype:(HbA/HbS)
Phenotype: Mixed hemoglobin (most red blood cells are normal, but some become sickle-shaped under stress).
Survivability:
Without malaria: Normal survivability.
With malaria: Best survivability due to partial protection against malaria.
Phenotypes and Genotypes and Survivability:
Sickle Cell Anemia
Genotype: (HbS/HbS)
Phenotype: Severe anemia; most red blood cells are sickle-shaped.
Survivability:
Without malaria: Low survivability due to health complications.
With malaria: Low survivability despite partial resistance to malaria, as health complications outweigh the advantage.
Effect of Environment on Allele Frequency
In malaria-endemic regions:
the HbA/HbS genotype has a selective advantage, leading to:
- Increased frequency of HbS allele.
- Balancing selection maintains both HbA and HbS alleles in the population.
Effect of Environment on Allele Frequency In regions without malaria:
there is no advantage to the HbS allele:
Natural selection reduces the HbS allele frequency over generations due to health disadvantages in HbS/HbS individuals.
Vector for Malaria
Malaria is caused by the Plasmodium parasite, transmitted through the Anopheles mosquito.
Impact of Malaria on Shaping Human Populations in Africa, Mediterranean, and Southeast Asia
Driven the evolution of genetic traits like sickle cell trait, G6PD deficiency, and beta-thalassemia, which offer resistance to malaria.
Increased the prevalence of these traits in populations despite health complications associated with homozygous conditions.
