There would be 25 chromosomes in the organism's sex cells, also called gametes.
This is because, during sexual reproduction, two gametes unite to form a zygote. Their chromosomes in this case combine to make 50. (Humans have 46 chromosomes in their body cells and 23 in their gametes.)
In short, the number of chromosomes in the gamete is half the number of chromosomes in the body cells.
