How many sperm cells are formed from an original cell in a drosophila fruit fly at the conclusion of meiosis?

Four sperm cells.

Explanation:

Meiosis is is a cell division process that generates four haploid cells (gametes) from a single diploid germline cell. In males, meiosis is part of spermatogenesis, the process to generate sperm. Sperm are the haploid cells that are generated in meiosis.

Meiosis is a highly conserved cell division process in eukaryotes that produces 4 cells (gametes) from a single cell (mother). However, Nondisjunction in male of Drosophila causes frequently sperm with a gain or loss of chromosomes.