Answer to Question #175387 in Evolution for Syd

Question

Demonstrate why sickle cell anemia could not have been a Mendelian dominant disease.

 Hint: See data below for the prevalence of the sickle cell anemia allele in various malaria zones.

 

Group

Unaffected

Carriers

Affected

Nigerians

0.739

0.240

0.019

S. Arabians

0.774

0.211

0.014

Greeks

0.774

0.211

0.014

 

Hint: Consider the general model for selection: Dq = ((pqw₁₂ + q² w₂₂)/w_avg) – q ; where average fitness (w_avg ) = p²w₁₁ + 2pqw₁₂ + q22w₂₂ and remember that w₁₁ is the fitness of genotype p2; w₁₂ is the fitness of genotype 2pq, and w₂₂ is the fitness of genotype q².

 

Hint: Use Python or Scrip to stimulate the generational model where the disease allele is dominant (and has lowest fitness) and compare that to when the allele is recessive and has lowest fitness. Finally, consider when the allele is recessive, but the heterozygote has higher fitness than either homozygote. Which simulation best fits the observed data?

Answer 1

The sickle cell anemia should not have been categorized as Mendelian inheritance disease, since it does not follow the law of dominance. Single recessive mutation cause sickle cell anaemia. The carriers of the sickle cell anaemia are resistant to malaria..