A monoclonal antibody differs from a polyclonal antibody in that monoclonal antibodies .

Options

A. are labeled with chemicals that can be visualized .
B. are produced by cells from the same organism that produced the antigen.
C. are synthesized by population of identical , or "cloned", cells .
D. are synthesized only in living organisms.

Answer

### Step-by-Step Solution:

1. **Definition of Monoclonal Antibodies**:
- Monoclonal antibodies are antibodies that are produced by identical immune cells (clones) that are all derived from a unique parent cell. This means they are specific to a single epitope on an antigen.

2. **Definition of Polyclonal Antibodies**:
- Polyclonal antibodies are produced by different B cell lineages in the body. They are a mixture of antibodies that recognize multiple epitopes on the same antigen.

3. **Specificity**:
- Monoclonal antibodies are monovalent, meaning they bind to one specific epitope. In contrast, polyclonal antibodies can bind to multiple epitopes on the same antigen due to their diverse origins.

4. **Production**:
- Monoclonal antibodies are synthesized by a population of identical or cloned cells. This is achieved through a process called hybridoma technology, where a single B cell is fused with a myeloma cell to produce a hybrid cell that can replicate indefinitely.
- Polyclonal antibodies are produced by different B cells responding to the same antigen, resulting in a heterogeneous mixture of antibodies.

5. **Source**:
- Monoclonal antibodies can be produced in vitro (in the lab) and can come from different species, while polyclonal antibodies are typically produced in vivo (within a living organism) and are a natural response to an antigen.

6. **Applications**:
- Monoclonal antibodies are often used in therapeutic applications and diagnostics due to their specificity, while polyclonal antibodies are used in research and can be less specific.

### Conclusion:
Monoclonal antibodies differ from polyclonal antibodies primarily in their specificity, production method, and source. Monoclonal antibodies are derived from a single clone of B cells and are specific to one epitope, whereas polyclonal antibodies are a mixture from different B cells that can bind to multiple epitopes.

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