The first recombinant DNA was constructed by

Options

A. Stanely Cohen and Herbert Boyer
B. Arber, Nathan and Smith
C. Fleming and Berg
D. Joshua Leaderberg

Answer

### Step-by-Step Solution:

1. **Understanding the Question**: The question asks about the first individuals who constructed recombinant DNA.

2. **Identifying Key Individuals**: From the options provided, we need to identify who among Stanley Cohen, Herbert Boyer, Arber, Nathan, Smith, Flamming, Berg, and Joshua Lederberg was responsible for the first construction of recombinant DNA.

3. **Recalling Historical Context**: It is essential to recall that recombinant DNA technology involves combining DNA from two different species to create a new genetic sequence.

4. **Identifying the Correct Answer**: According to the information provided, the first recombinant DNA was constructed by Stanley Cohen and Herbert Boyer. They are credited with pioneering work in this area.

5. **Understanding Their Contribution**: Cohen and Boyer's work involved the combination of DNA from different organisms, which laid the foundation for modern genetic engineering.

6. **Conclusion**: Therefore, the answer to the question is that the first recombinant DNA was constructed by Stanley Cohen and Herbert Boyer.