Sickle Cell Anemia (SCA)

Question 1

Which researchers elucidated the SCA disease

Answer 1

James, B Herrick and Lewis Pauling

Question 2

What of inheritance is observed with SCA

Answer 2

Autosomal recessive.
Hetros have sickle cell trait. Slight deformaty in hetros, not enough to not function
Sickle cell trait people are immune to malaria

Question 3

What is the result of inheriting the sickle cell gene

Answer 3

Collapse of the red blood cell due to the presence of long chain of HbS polymer in the haemoglobin.
RBC go doughnut shape to cell with flayed and jagged edges

Question 4

What mutation leads to the SCA

Answer 4

Single Nucleotide Polymorphism (SNP) 11p15:
GAC to GTC.
Transcription of GTC to GUG
Glutamate is replaced with valine at position 6 (7 counting methionine) in beta-globin gene
Valine is hydrophobic, hydrophobic regions of deoxyHb polymerise

Question 5

Why is the valine residue so disruptive

Answer 5

At low partial pressure of O2, deoxyhaemoglobin exposes hydrophic patches.
Hydrophic valine between E and F helices are able to aggregate and form fibrous precipitate.

Question 6

Why is SCA so prevalent

Answer 6

Carriers have RBC that can not be infected by malaria mosquitos
Malaria enters RBC but burst immediately preventing the virus from reproducing
Aggregation of Hb prevents virus from reproducing

Therefore, allele is selected for as seen with prevalence in malaria affected regions of sub-saharan Africa

Question 7

Possible treatment/ research

Answer 7

TBC