Which of the following correctly defines a transgenic animal

Options

A. An animal which has foreign DNA and RNA in some of its cells because of an injection of DNA and RNA into the nucleus of the zygote from which it is developed
B. An animal which has foreign DNA in all its cells because of an injection of DNA into the nucleus of the zygote from which it is developed
C. An animal which has foreign DNA in some of its cells because of an injection of DNA into the nuclei of some of the cells of the blastocyst
D. An animal which has foreign DNA in all its cells because of an injection of DNA into the nuclei of some of the cells in adulthood

Explanation

### Step-by-Step Solution:

1. **Understanding Transgenic Animals**:
- Transgenic animals are organisms that have had a foreign gene deliberately inserted into their genome. The term "transgenic" comes from "trans," meaning transformed, and "genic," referring to genes.

2. **Role of Genetic Material**:
- The primary genetic material in animals is DNA (deoxyribonucleic acid). In transgenic animals, a foreign gene is introduced into the DNA using recombinant DNA technology.

3. **Insertion of Foreign Gene**:
- The foreign gene is typically inserted at the zygote stage, which is the earliest developmental stage of the organism. This ensures that the foreign gene is present in all cells as the organism develops.

4. **Expression of the Foreign Gene**:
- Once the foreign gene is integrated into the animal's genome, it can be expressed, leading to the production of a new protein. This protein can confer new traits or characteristics to the animal, such as producing a specific protein in its milk.

5. **Evaluating the Options**:
- Now, let's analyze the provided options to find the correct definition of a transgenic animal:
- **Option 1**: An animal that has foreign DNA and RNA in some of its cells. (Incorrect, as RNA is not the primary genetic material in animals.)
- **Option 2**: An animal that has foreign DNA in all of its cells because of an injection of DNA into the nucleus of the zygote from which it is developed. (Correct, as this accurately describes the process of creating a transgenic animal.)
- **Option 3**: An animal that has foreign DNA in some of its cells. (Incorrect, as the presence of foreign DNA in only some cells would not guarantee expression of the new trait.)
- **Option 4**: An animal that has foreign DNA in all its cells because of an injection of DNA into the nucleus of some of the cells in adulthood. (Incorrect, as transgenic modifications are typically done at the zygote stage, not in adult cells.)

6. **Conclusion**:
- The correct definition of a transgenic animal is given in **Option 2**.