Evaluate the gel provided below. Use the notes to help you read the gel: DNA is loaded in the wells (little pockets) at the top. The wells are the dark spaces under the numbers. DNA moves from the wells into the gel. The smaller the DNA the more quickly it moves. The samples on the ends are DNA ladders. We know the sizes of each of those bands and can use them to estimate the size of the DNA in the patient samples.

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**Evaluating Gel Electrophoresis Results**

**Image Description:**
The gel image shows DNA samples loaded at the top, with bands visible under each numbered lane. The samples are:

1. **DNA Ladder**: Used as a reference to estimate DNA size.
2. **Positive Control**: Ensures the test can detect DNA.
3. **Patient 1 Sample**
4. **Patient 2 Sample**
5. **Patient 3 Sample**
6. **Negative Control**: Ensures no contamination.
7. **DNA Ladder**

**Band Sizes:**
- The ladder indicates sizes from 100 bp to 300 bp.
- Bands within the patient samples can be compared to the ladder for size estimation.

**Questions:**

1. **Why are positive and negative controls needed for PCR (or any test)?**
   - Positive controls confirm the test works correctly by producing expected results. Negative controls ensure no contamination affects the results.

2. **Initially, test kits sent out by the CDC were flawed. The negative control sometimes showed up as positive. What misdiagnosis would potentially occur with this mistake? (Over or underdiagnosis?)**
   - An incorrect positive result for the negative control could lead to overdiagnosis, as it falsely indicates the presence of the target DNA.

3. **The CDC ultimately said to use the test anyway. Why might this be the case, given the current situation?**
   - Despite some flaws, the test might still provide useful information in a critical situation where timely data is crucial for public health responses.

4. **How would you evaluate the results above? Do any of the patients have SARS-CoV-2?**
   - Compare patient sample bands against the positive and negative controls. If a patient sample mirrors the positive control, it suggests a positive result. In this image, Patient 1 and Patient 2 have bands similar to the positive control, indicating potential SARS-CoV-2 presence. Patient 3 does not show such a band, resembling the negative control instead.
Transcribed Image Text:**Evaluating Gel Electrophoresis Results** **Image Description:** The gel image shows DNA samples loaded at the top, with bands visible under each numbered lane. The samples are: 1. **DNA Ladder**: Used as a reference to estimate DNA size. 2. **Positive Control**: Ensures the test can detect DNA. 3. **Patient 1 Sample** 4. **Patient 2 Sample** 5. **Patient 3 Sample** 6. **Negative Control**: Ensures no contamination. 7. **DNA Ladder** **Band Sizes:** - The ladder indicates sizes from 100 bp to 300 bp. - Bands within the patient samples can be compared to the ladder for size estimation. **Questions:** 1. **Why are positive and negative controls needed for PCR (or any test)?** - Positive controls confirm the test works correctly by producing expected results. Negative controls ensure no contamination affects the results. 2. **Initially, test kits sent out by the CDC were flawed. The negative control sometimes showed up as positive. What misdiagnosis would potentially occur with this mistake? (Over or underdiagnosis?)** - An incorrect positive result for the negative control could lead to overdiagnosis, as it falsely indicates the presence of the target DNA. 3. **The CDC ultimately said to use the test anyway. Why might this be the case, given the current situation?** - Despite some flaws, the test might still provide useful information in a critical situation where timely data is crucial for public health responses. 4. **How would you evaluate the results above? Do any of the patients have SARS-CoV-2?** - Compare patient sample bands against the positive and negative controls. If a patient sample mirrors the positive control, it suggests a positive result. In this image, Patient 1 and Patient 2 have bands similar to the positive control, indicating potential SARS-CoV-2 presence. Patient 3 does not show such a band, resembling the negative control instead.
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