Which of the following techniques cannot be used to determine the genetic defect of an embryo?

Options

A. Ultrasound
B. CVS
C. PUBS
D. Amniocentesis

Answer

To determine which technique cannot be used to identify genetic defects in an embryo, we will analyze each option provided in the question.

### Step-by-Step Solution:

1. **Understanding the Techniques**:
- We have four techniques to evaluate: ultrasound, CVS (Chorionic Villus Sampling), PUBS (Percutaneous Umbilical Blood Sampling), and amniocentesis.

2. **Analyzing Ultrasound**:
- **Ultrasound**: This is an imaging technique primarily used to monitor the growth and development of the fetus. It provides images of the fetus and can help assess the physical development of organs and structures. However, it does not provide information about genetic defects. Therefore, it cannot be used to determine genetic defects.

3. **Analyzing CVS**:
- **Chorionic Villus Sampling (CVS)**: This is an invasive procedure where a small sample of placental tissue is taken for genetic testing. This technique can identify genetic defects, making it a valid method for this purpose.

4. **Analyzing PUBS**:
- **Percutaneous Umbilical Blood Sampling (PUBS)**: This technique involves taking a blood sample from the umbilical cord. It is also used for genetic testing and can identify genetic defects. Thus, it is a valid method.

5. **Analyzing Amniocentesis**:
- **Amniocentesis**: This is a procedure where amniotic fluid is sampled from the amniotic cavity. The fluid contains fetal cells that can be analyzed for genetic defects. Therefore, this technique can also be used to determine genetic defects.

6. **Conclusion**:
- After analyzing all the techniques, we conclude that the only technique that cannot be used to determine genetic defects in an embryo is **ultrasound**.

### Final Answer:
**Ultrasound cannot be used to determine the genetic defect of an embryo.**

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