How many ribs does each gender have?

men and women both have 24 ribs - 12 on each side.  The first seven pairs of ribs are connected to the sternum (breast bone). Rarely, some pople have one more or less pairs of ribs due to various genetic mutations.

I just wanted to add a little on the source of the misconception. In the Biblical story of Adam and Eve, God made Eve from one of Adam's ribs, and this is why the myth that men have one fewer rib than women begun. When the Flemish anatomist Vesalius identified the fact that both men and women had the same number of ribs in 1543 it set off a wave of controversy. Amazingly, the myth is still propagated today, over 450 years after it was disproven.

Just to ad to Sarda's comment, there have been suggestions that the 'rib' in the Biblical story may refer to the baculum, or penis bone, which is present in other primates and many other mammals, but not in humans.

The problem with just-so stories of this kind is that they are usually invented as an explanation for an observation, but the observation is then used as evidence to support the story, which is circular logic.