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Importance of sickle cell gene against malaria

You have been studying genetic transmission and should be aware of law of dominance in gene expression pattern.

Studies have shown that sometimes being a carrier for a certain disease is advantageous over being affected or completely healthy for that gene. Sickle-cell anemia (SCA) is an example of this kind of ‘heterozygote advantage’ in certain populations.

SCA is a genetic blood disorder when hemoglobin has abnormal sickle shape. Hemoglobin S (HbS) is a variant form of normal hemoglobin (HbA) gene and is very common in Africa. Interestingly, heterozygotes for that gene (HbAS) are in positive selection in those regions compared to homozygotes (HbSS) and are more protected from malaria morbidity/mortality (see image).

Malaria transmision HbAA HbAS HbSS Malaria infection Malaria mortality

Part I. Fill in the blanks (copy/paste the table in your reply)

Genetic make up of individual

Characteristic of individual

Outcome with no malarial infection

Outcome with malarial infection


Dies young


Sickle cell trait



Part II. Respond with a minimum of 150 words.

Please describe some ways in which being a SCA carrier can be advantageous and disadvantageous. What are some reasons why the SCA allele frequency is higher in Africa than in America?

Part III. Respond to your peers (two replies are required).

Replies should be substantive and reflect that the student read and thought about the assigned reading and additional sources posted by the person they are replying to.

The reply post meets the word requirement of 100 to 150 words.

The reply moves the conversation forward or makes a reply to a question asked in response to their own posting.

Replies are made over several days rather than all crammed into the due dates.

Here is a paper by Williams and Obaro on SCA and malaria:


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