Mystery of the Crooked Cell

The crescent, or sickle, shape is due to a mutation in the gene that codes for a protein in red blood cells which binds to oxygen. The mutation codes for a specific amino acid that results in a mutated hemoglobin protein called valine, which is hydrophobic. This hydrophobia causes the sickle shape of the red blood cell.

Normal Hemoglobin: This phenotype occurs when an individual has two wild alleles (in this lab, we represent this genotype as NN).

Sickle Hemoglobin: This phenotype only occurs when an individual receives two mutated alleles (represented as SS).

Carrier: An individual who receives one normal and one sickle allele from their parents is a carrier for sickle cell anemia (genotype represented as NS). A carrier may go into “sickle cell crisis,” experiencing the symptoms of sickle cell under severe circumstances. However, a sickle cell carrier is also more resistant to the infectious disease malaria.

Pre-Lab Questions:

• What causes sickle cell anemia and how is it passed through genetics?
• What is the difference between being heterozygous for a gene and homozygous for a gene?
• What is the difference between a genotype and a phenotype?

Click here for the Pre-lab Classroom Activity for a group activity investigating patient history, manipulating models of alleles, and gathering evidence to aid in discussion of sickle cell anemia.

A local high school football player was rushed to the hospital after collapsing on the field. The player reported to the emergency room physician, Dr. James Herrick, that he had experienced similar symptoms multiple times during his childhood. These symptoms include extreme fatigue after non-strenuous exercise, being unusually short of breath, extreme pain in his joints and muscles, a yellowish tint in the whites of his eyes, and tenderness in his abdomen. Consequently, the patient would often have to spend time in bed after a “crisis”.

A look at his immediate family history reveals that neither of his parents have had similar symptoms. However, upon further investigation, it is revealed that the patient’s paternal uncle and grandmother shared the same symptoms under the same circumstances. Based on this medical history, Dr. Herrick believes the patient may have sickle cell anemia.

Dr. Herrick has asked for your help in confirming his diagnosis. To do so, you will be testing the patient’s hemoglobin protein using gel electrophoresis. Based on your results, you can then confirm the patient’s diagnosis.

Click here to see our Post-Lab Classroom Activity, with discussion prompts and real-world applications to the sickle cell lab.