Difference Between SS and SC Genotype

Main Difference – SS vs SC genotype

SS and SC are two genotypes that produce defective red blood cells in humans. Typically, red blood cells are disc-shaped cells, comprising hemoglobin to carry oxygen throughout the body. Three hemoglobin alleles can be identified in humans; these determine the genotype of hemoglobin. They are A, S, and C. The allele A is the wild-type allele whereas S is the sickle cell allele. The three alleles produce three types of hemoglobin; hemoglobin A, hemoglobin S, and hemoglobin C, respectively. The difference between them is the type of amino acid present in the sixth position of the hemoglobin chain. Since humans have two alleles of a particular gene, two hemoglobin alleles are present as well. Therefore, six different allele combinations can be found in humans: AA, AS, AC, CC, SS, and SC. Both SS and SC contain the sickle cell allele. They differ by the symptoms observed in humans. The main difference between SS and SC genotype is that SS is the genotype that produces the sickle cell disease whereas SC causes recurrent anemia.

Key Areas Covered

1. What is SS
      – Definition, Characteristics, Function
2. What is SC
      – Definition, Characteristics, Function
3. What are the Similarities Between SS and SC Genotype
      – Outline of Common Features
4. What is the Difference Between SS and SC Genotype
      – Comparison of Key Differences

Key Terms: Anemia, Genotype, Hemoglobin, Red Blood Cells, Retinopathy, SC, Sickle Cell Disease, Sickle Cell-Hemoglobin C disease, SS

Difference Between SS and SC Genotype - Comparison Summary

What is SS

SS refers to the hemoglobin genotype that causes sickle cell anemia. The SS genotype consists of two sickle cell alleles (S). Each allele is inherited from each parent. The S allele shows some resistance to malaria. The S allele produces a globin chain with a valine in its sixth position. The wild-type allele for hemoglobin is allele A and it produces a globin chain with a glutamine at its sixth amino acid position. Hemoglobin is formed by a combination of two globin proteins. The wild-type hemoglobin is called hemoglobin A. Hemoglobin A produces normal, disk-shaped red blood cells, which are flexible enough to travel through small blood vessels. The S allele produces hemoglobin S. The red blood cells produced by hemoglobin S are crescent-shaped. These red blood cells are sticky and rigid. They clump together, resulting in blockages of the blood flow. This causes pain crises, bone degeneration, and prolonged, painful erections called priapism. This situation is called the sickle cell disease.

Difference Between SS and SC

Figure 1: Normal and Sickle Cell Red Blood Cells

The symptoms of the sickle cell disease are described below.

  • Excessive fatigue from anemia
  • Fussiness in babies
  • Bedwetting from associated kidney problems
  • Jaundice
  • Frequent infections
  • Swelling and pain in hands and feet
  • Pain in chest and back

What is SC

SC refers to another abnormal genotype of hemoglobin that causes recurrent anemia. The genotype SC is produced by one S and one C allele. The C allele is also a mutant allele type, producing an abnormal hemoglobin called hemoglobin C. SC genotype is called sickle cell-hemoglobin C. It is also called hemoglobinopathy. This situation causes less blood clumping than sickle cell disease. Therefore, people with SC genotype have fewer pain crises than people with genotype SS. However, they experience significant bone degeneration, especially in the bones in the hip. They also experience degradation of the retina, which is known as retinopathy. Retinopathy is caused by less oxygen supply to the eye. More blood vessels form around the eye to face this situation. The stained blood smears of the genotype SC exhibit sphere-shaped red blood cells (spherocytes) and rarely sickle cells.

Main Difference -  SS vs  SC

Figure 2: Spherocytes

The symptoms of the sickle cell-hemoglobin C disease are described below.

  • Recurrent anemia
  • Jaundice
  • Infection of the blood (septicemia)
  • Sudden enlargement of the spleen
  • Sudden pain and fever
  • Swelling of hands and feet
  • Chest pain and troubles of breathing
  • Pneumonia
  • Stroke
  • Blood in urine
  • Leg ulcers
  • Gallstones
  • Vision problems
  • Organ damage and kidney failures
  • Painful erections
  • Problems in pregnancy

Similarities Between SS and SC Genotype

  • Both SS and SC consist of sickle cell alleles.
  • Both SS and SC genotypes produce defective red blood cells.
  • Both SS and SC genotypes produce signs and symptoms related to red blood cells.
  • Both SS and SC may cause sickle cell anemia.

Difference Between SS and SC Genotype


SS: SS refers to the genotype that causes sickle cell disease (SCD).

SC: SC refers to the genotype that causes a type of SCD with less intense symptoms.

Amino Acid Composition

SS: The genotype SS consists of valine in the sixth position of both amino acid chains.

SC: The genotype SC consists of valine and lysine in the sixth position of both amino acid chains.

Number of Sickle Cell Alleles

SS: The SS genotype consists two sickle cell alleles.

SC: The SC genotype consists of one sickle cell allele.

Signs and Symptoms

SS: The SS genotype produces sickle cell anemia.

SC: The SC genotype produces recurrent anemia, vaso-occlusive crises, and aseptic necrosis of the thigh bone.


SS: The genotype SS shows a significant resistance to malaria.

SC: The genotype SC does not show a slight resistance to malaria.


SS and SC are two genotypes of hemoglobin that cause abnormal red blood cells. The genotype SS produces hemoglobin S in the red blood cells, which easily clump inside the blood vessels. This causes sickle cell disease. The genotype SC produces both hemoglobin S and hemoglobin C in the red blood cells. This causes sickle cell-hemoglobin C disease. The symptoms of sickle cell-hemoglobin C disease are less severe than the symptoms of sickle cell disease. The main difference between SS and SC is the symptoms caused by each genotype.


1. “Sickle Cell Anemia.” Healthline, Healthline Media, 29 Mar. 2017, Available here. Accessed 9 Sept. 2017.
2. “Hemoglobin SC disease.” Genetic and Rare Diseases Information Center, U.S. Department of Health and Human Services, Available here. Accessed 9 Sept. 2017.

Image Courtesy:

1. “Sickle cell 01” By The National Heart, Lung, and Blood Institute (NHLBI) – (Public Domain) via Commons Wikimedia
2. “ww325 spherocyte” by isis325 (CC BY 2.0) via Flickr

About the Author: Lakna

Lakna, a graduate in Molecular Biology and Biochemistry, is a Molecular Biologist and has a broad and keen interest in the discovery of nature related things. She has a keen interest in writing articles regarding science.

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