Italian IMAT Q23

  1. Sickle cell anaemia is a human genetic disease that occurs in individuals homozygous for the autosomal recessive HbS allele. Sickle cell anaemia is fatal if left untreated. Which of the following statements is wrong?

A. The HbS allele, since in homozygosity, it causes a lethal pathological condition, has a low frequency in all human populations.
B. The HbS allele differs from the wild type allele by a point mutation affecting a single nucleotide.
C. The change of an amino acid resulting from the point mutation leads, in lack of oxygen, to hydrophobic interactions in the molecules of Y-globin
D. Heterozygous individuals in malaria prone populations have a major probability of survival.
E. The advantage of heterozygotes in malarial areas keeps relatively high (15 to 20 per cent) the frequency of the HbS allele

I understand why A is wrong - because the homozygosity can’t mean it has a low frequency in ALL human populations but could someone explain the reasoning behind the other options. Is the link to malaria something to do with the blood (mosquitos drink the blood??) I have no idea, but if someone could explain this to me and if we need to know these details for the exam.

thank you!!


Sickle cell anemia does help prevent malaria since the abnormally shaped RCB make it difficult for the parasites inside the cells to have a functional reproductive cycle I believe?

When a question pop up and seem outside of the scope of the IMAT, they don’t expect us to know the answer but figure it out with past knowledge and reasoning skills

There can only be one wrong answer, but both D) and E) relate to the fact that sickle cell prevents infection so this statement must be correct

A) directly contradicts this since and advantageous mutation is most likely to be passed on


Thank you Juliette! So I just have to look for the wrong one if we don’t know, thank you so much!!