Taylor and his colleagues proved the semi - conservative model of replication by performing experiments on ………(a) …………. Using (b) ……….

Options

A. `{:((a),"(b)"),("Bacteriophage","radioactive thymidine"):}`
B. `{:((a),"(b)"),("E. coli","radioactive nitrogen "):}`
C. `{:((a),"(b)"),("Vicia faba","radioactive nitrogen "):}`
D. `{:((a),"(b)"),("E. coli","heavy nitrogen "):}`

Answer

To answer the question regarding Taylor and his colleagues' experiments that proved the semi-conservative model of DNA replication, we can break it down into the following steps:

### Step-by-Step Solution:

1. **Identify the Organism Used in the Experiment:**
- Taylor and his colleagues conducted their experiments on **Vicia faba**, commonly known as faba beans. This plant was chosen because it has a well-defined chromosomal structure, which is suitable for studying DNA replication.

2. **Identify the Substance Used in the Experiment:**
- In their experiments, Taylor and his colleagues used **radioactive thymidine**. Thymidine is a nucleoside that contains the nitrogenous base thymine, which is a component of DNA. The radioactive form allowed them to trace the incorporation of thymidine into the DNA during replication.

3. **Understanding Semi-Conservative Replication:**
- The semi-conservative model of DNA replication states that during the replication process, each new DNA molecule consists of one old (template) strand and one newly synthesized strand. This was demonstrated through the experiments by observing the incorporation of radioactive thymidine into the DNA of the faba beans.

4. **Conclusion:**
- Therefore, the correct completion of the statement is:
- Taylor and his colleagues proved the semi-conservative model of replication by performing experiments on **Vicia faba** using **radioactive thymidine**.

### Final Answer:
Taylor and his colleagues proved the semi-conservative model of replication by performing experiments on **Vicia faba** using **radioactive thymidine**.

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