Haploinsufficient genes are genes that require two functional copies for normal function. When one copy is lost or mutated, the remaining functional copy is not enough to maintain the necessary biological activity. This can lead to various health issues or developmental problems, as the reduced gene dosage fails to meet the cellular demands. In humans, haploinsufficiency is often associated with certain genetic disorders. For example, mutations in the TP53 gene, which is crucial for tumor suppression, can result in increased cancer risk due to haploinsufficiency. Understanding these genes is important for genetic research and potential therapeutic approaches.