The type of horizontal gene transfer in prokaryotes where a cell receives DNA from another through sex pili is called conjugation.

Here's a breakdown:

* Horizontal gene transfer (HGT): The transfer of genetic material between organisms that are not related by descent. This is in contrast to vertical gene transfer, where genes are passed down from parent to offspring.

* Conjugation: A process where a bacterium with a fertility plasmid (F factor) forms a pilus, a thin, hair-like structure, that attaches to a recipient bacterium. The F factor carries genes that allow the formation of pili, and it can be transferred to the recipient bacterium through the pilus. This transfer can also include other bacterial DNA, such as chromosomal DNA.

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