* Clones are genetically identical copies of an organism or cell. Cell cultures are often created from a single parent cell, and all the cells in the culture are descendants of that original cell.

Let's look at the other options:

* Vectors are tools used to carry genetic material into cells, like viruses or plasmids. They don't directly relate to genetic sameness within a culture.

* Plasmids are small, circular DNA molecules found in bacteria. While they can be used in genetic engineering, they don't explain why cells in a culture are genetically similar.

* Hybrids are organisms created by combining genetic material from two different sources. This is not the case in a typical cell culture.

In summary: Cells in a cell culture are genetically identical because they are all descendants of the same original cell, making them clones.