Transgenic animals
Transgenic animals are animals that have had their DNA manipulated to possess and express an extra gene. This process involves the introduction of foreign DNA into the genome of the animal, which can be done through various techniques such as pronuclear injection, embryonic stem cell-based gene transfer, or viral vectors.

Explanation:
Transgenic animals are created by introducing a specific gene into the DNA of an animal. This gene can come from the same species or a different species altogether. The purpose of this manipulation is to alter the genetic makeup of the animal and enable it to express certain traits or produce specific proteins.

Advantages of transgenic animals:
- Transgenic animals are often used in scientific research to study the functions of specific genes and their effects on biological processes. By introducing a gene into an animal, researchers can observe the effects it has on the animal's development, physiology, and behavior.
- Transgenic animals can be used to produce valuable proteins, such as human insulin or growth hormones, in large quantities. These proteins can then be harvested and used for medical purposes.
- Transgenic animals can also be used to study and model human diseases. By introducing genes associated with a particular disease into an animal, researchers can observe the development and progression of the disease and test potential treatments.

Examples of transgenic animals:
- The first transgenic animal, a mouse, was created in the early 1980s. Since then, various other animals have been genetically modified, including rats, rabbits, pigs, sheep, cows, and even primates.
- Transgenic mice are commonly used in scientific research due to their relatively short generation time and ease of manipulation.
- Transgenic pigs have been developed with the aim of producing organs suitable for transplantation into humans, known as xenotransplantation.
- Transgenic goats have been modified to produce spider silk proteins in their milk, which can be used to create strong and flexible materials.

In conclusion, transgenic animals refer to animals that have had their DNA manipulated to possess and express an additional gene. This process has numerous applications in scientific research, medicine, and industry, and has led to significant advancements in our understanding of genetics and the development of new therapies and materials.