SCA _ 1111

SCA & Meiosis

Mice & SCA

SCD Symptoms & Treatments

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SCA Statistics

Dr. KT Lemon

The Genetics Behind SCA

The Inheritance Pattern of SCA

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SCA & The Mitochondrion

Sickle Cell Anemia

Sickle Cell Anemia (SCA)

Hemoglobin is shown above. It has four subunits, two alpha chains, and two beta chains.

• Sickle cell anemia is an autosomal recessive disorder.

• People who have SCA have abnormal hemoglobin, a protein that carries oxygen.

• The abnormal protein is produced because of mutations in the HBB gene.

Effects of the Mutation

• The RBCs become sickled.
• The sickled cells block blood flow and die early, leading to anemia.

• Common symptoms experienced by people with SCA include shortness of breath, fatigue, delayed growth and development, fatigue, jaundice, and painful swelling in the hands and feet.

• The single nucleotide change in the HBB gene causes the production of valine, a hydrophobic amino acid, thereby changing the function of the hemoglobin Beta protein.
• The original DNA codon and its product can be seen in the diagram.

The Genetics Behind SCA

A blood test can diagnose SCA as shown above.

SCA is the only condition that utilizes two different letters to represent the genotype.

• A = represents normal hemoglobin
• S = represents abnormal hemoglobin

The Genotype of SCA

NOTE- SCA is the only condition that utilizes two different letters to represent genotype.

Pedigree Details

• I-1 is a male who is a carrier. His genotype is AS.
• I-2 is a female who is a carrier. Her genotype is AS.
• They have three children, II-2 (female with SCA; genotype SS), II-3 (male carrier; genotype AS), and II-4 (normal female; genotype- AA).
• II-2 is married to II-1 (normal male; genotype AA).
• They have one child, III-1 (carrier male; genotype AS).

Pedigree of SCA

• SCA is inherited in an autosomal recessive pattern
• Two bad copies of the HBB gene are needed for an individual to develop SCA.
• Individuals with hemoglobin S and A are considered carriers of the SCA trait.

The Inheritance Pattern of SCA

• The pedigree shown can be used to showcase how SCA is associated with meiosis.
• I-1 produced the sperm cell partially responsible for producing II-2. That sperm cell carried one mutated copy of the HBB gene.
• I-2 produced the egg cell partially responsible for producing II-2. It too carried one mutated copy of the HBB gene.
• The result of the two sex cells uniting was a girl who had sickle cell anemia.

Pedigree of SCA

• SCA is a genetic disorder that is inherited through meiosis.
• This is because meiosis is the process of cell division that creates gametes.
• The diagram to the right depicts the two gametes produced during meiosis and the process of creating a diploid organism.

SCA & Meiosis

A 3D rendering of mitochondria (red) inside a sickled RBC

In patients who have SCA, mature RBCs maintain their mitochondria(the red structures).

Normally, mitochondria are lost when RBCs mature.

SCA & Mitochondria

Mitochondria are specialized organelles responsible for cellular energy production.

Mus musculus (house mouse) are commonly used model organisms in genetic research.

• Researchers have created a transgenic mouse model of sickle cell using Mus musculus to detail the pathophysiology of the disease and to assist in the development of treatment options for SCA.
• A transgenic organism carries a foreign gene that has been deliberately inserted into its genome. The foreign gene is constructed using recombinant DNA methodology.

SCA & the Model Mouse

Now that you completed the interactive infographic, navigate to the quiz on GAVIEW.

SCA Quiz