Which of the following best describes cloning?

Cloning is best described as the duplication and propagation of a cell or organism. This process involves creating a genetically identical copy of a particular cell or organism, thereby producing offspring that carry the same genetic material as the original. In a laboratory setting, cloning can be performed using techniques such as somatic cell nuclear transfer or DNA cloning, where a specific piece of DNA is replicated, leading to the generation of multiple identical copies.

The notion of cloning encompasses not just the creation of whole organisms but also the replication of specific cells or genes, allowing for a consistent genetic makeup in the resulting organisms or cells. This concept is fundamental in various biotechnological applications, including the production of genetically modified organisms, stem cell research, and therapeutic cloning.

The other options refer to distinct biological concepts. Inserting foreign DNA into a host organism pertains to genetic engineering rather than cloning itself. Transforming one type of cell into another generally relates to cellular differentiation and genetics, while measuring genetic expression is associated with understanding how genes are turned on and off, which is critical to gene regulation but does not inherently involve cloning.