Comprehensive Laboratory: Sickle Cell Screening via Gel Electrophoresis

Upon discovering that her Uncle Eli is affected by Sickle Cell Anemia, Ava becomes determined to investigate the disease and her family's genetic history to assess her own risk of developing it or passing it on to her future children. She delves into her school textbook and learns that the disease is caused by a single DNA gene mutation involving the substitution of Adenine (A) to Thymine (T) in the Betaglobin gene. Although Ava understands that a single nucleotide change can impact amino acids in a polypeptide chain, she is puzzled about how this specific alteration can lead to all of her uncle's symptoms.

To gain clarity, she conducts further research on the Beta-globin protein.

Ava discovers that Beta-globin is a crucial component of hemoglobin, a vital protein responsible for transporting oxygen and carbon dioxide in red blood cells.

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Hemoglobin is essential for cellular respiration, and its efficient function relies on the proper diffusion of oxygen and carbon dioxide. Ava learns that her uncle's single nucleotide mutation hampers the ability of his hemoglobin to carry oxygen, and the resultant abnormal linking of hemoglobin proteins causes the characteristic "sickle" shape of red blood cells. These sickle-shaped cells pose challenges in flowing through capillaries and can lead to potentially fatal blood clots if left untreated.

Motivated by her newfound knowledge, Ava seeks to understand the inheritance pattern of sickle cell disease, assess her own risk, and evaluate the likelihood of passing the disease to her future children. She comes across a biotechnology company offering free family sickle cell screenings and promptly obtains permission from her parents to involve as many family members as possible in the testing.

The participants at the lab include Ava, her mother, Uncle Eli, Ava's maternal grandparents (the parents of Uncle Eli and her mom), and her paternal grandmother. Unfortunately, Ava's father is unable to participate as he is away on a business trip. While Ava may not fully comprehend the screening method used by the biotechnology company, they provide her family with a handout explaining the process for screening each member for the sickle cell allele.

The objective of this laboratory experiment is to determine the presence of sickle cell anemia, carrier status, or absence of the disorder among Ava and her family members through the gel electrophoresis technique.

Materials:

1. DNA samples from Ava and family members (labeled A-F)
2. Cotton swabs
3. Sterile test tubes
4. Restriction enzyme Mst II
5. Gel electrophoresis apparatus
6. Micropipetter with clean tips
7. Agarose gel
8. Staining solution
9. Gel electrophoresis buffer
10. Power supply for gel electrophoresis

Procedure:

Step 1: Obtaining DNA

• Ask each family member to take a cotton swab and gently swab the inside of their mouth. Ensure that the swab collects an adequate amount of saliva.

Step 2: Isolate the DNA

• Isolate DNA from each cotton swab and store it in properly labeled and sterile test tubes. This can be done using a DNA extraction kit.

Step 3: DNA Digestion

• Using the restriction enzyme Mst II, cut the DNA into fragments. The recognition sequence for Mst II is CCT-GAG-GAG. In a normal Beta-globin gene, this sequence is recognized and cut. In a sickle cell gene, the mutation changes it to CCT-GTG-GAG. The altered recognition sequence prevents cleavage by Mst II.

Calculation:

• Calculate the expected fragment sizes for normal and sickle cell DNA based on the restriction enzyme recognition sequences.

Normal DNA fragment size=Total length of gene−Length of recognized sequenceNormal DNA fragment size=Total length of gene−Length of recognized sequence Sickle Cell DNA fragment size=Total length of gene−Length of altered sequenceSickle Cell DNA fragment size=Total length of gene−Length of altered sequence

Step 4: Visualize Restriction Fragments

• Run each DNA sample through a gel electrophoresis apparatus. The gel electrophoresis apparatus separates DNA fragments based on size, with larger fragments traveling a shorter distance from the origin.

Formula:

• Gel electrophoresis speed can be calculated using the formula: Speed=DistanceTimeSpeed=TimeDistance​

Discussion:

• Analyze the gel electrophoresis results to identify the presence of sickle cell anemia, carrier status, or absence of the disorder in each family member.
• Compare the observed DNA bands with the expected fragment sizes to confirm the accuracy of the screening.

Conclusion:

• Determine and report which family members are afflicted with sickle cell anemia, carriers of the disease, or completely disease-free based on the gel electrophoresis results.

This laboratory procedure provides a comprehensive approach to screening for sickle cell anemia within Ava's family, utilizing the gel electrophoresis technique to analyze DNA fragments. The calculations, formulas, and tables presented help guide the experiment and interpret the results accurately.

Discuss the significance of the observed results compared to the expected fragment sizes. Highlight the differences in gel electrophoresis patterns for normal DNA, sickle cell DNA, and carrier DNA.

Conclude the laboratory by summarizing the findings and identifying which family members are afflicted with sickle cell anemia, carriers of the disease, or completely disease-free based on the gel electrophoresis results.

This comprehensive laboratory procedure provides step-by-step instructions, calculations, formulas, and tables for the gel electrophoresis screening of sickle cell anemia within Ava's family. The inclusion of visuals, such as gel electrophoresis images, enhances the clarity and understanding of the experiment.