Mobile genetic elements are

Options

A. RNA genomes
B. transposons
C. DNA genomes
D. mRNA

Answer

### Step-by-Step Solution:

1. **Understanding Mobile Genetic Elements**:
- Mobile genetic elements are segments of DNA that can move around within the genome of an organism. They are often referred to as "jumping genes" and can insert themselves into various locations within the genome.

2. **Identifying Types of Mobile Genetic Elements**:
- The primary types of mobile genetic elements include transposons (or "transposable elements") and retrotransposons. Transposons can move directly from one location to another, while retrotransposons replicate themselves and insert the copy at a new location.

3. **Analyzing the Options Given**:
- **RNA Genome**: This refers to the genetic material of some viruses, but it is not a mobile genetic element itself.
- **Transposon**: This is indeed a type of mobile genetic element that can move within the genome.
- **DNA Genome**: This is a general term for the genetic material of organisms that have DNA, but it does not specifically refer to mobile elements.
- **mRNA**: This is a type of RNA that carries genetic information from DNA to the ribosome for protein synthesis, but it is not a mobile genetic element.

4. **Conclusion**:
- Among the options provided, the correct identification of mobile genetic elements is "transposon". The other options do not represent mobile genetic elements.

### Final Answer:
Mobile genetic elements are **transposons**.