haplodiploïdie

Haplodiploidy is a sex-determination system in which an individual's sex is determined by the number of sets of chromosomes they inherit. In this system, females develop from fertilized eggs and are diploid, meaning they have two sets of chromosomes. Males develop from unfertilized eggs and are haploid, possessing only one set of chromosomes. This system is found in many insect groups, including hymenopterans like ants, bees, and wasps, as well as in some other arthropods and even in some mites.

The genetic makeup of haplodiploid organisms leads to unique genetic relatedness patterns among siblings. Sisters are more closely related to each other than they would be in a diploid system. This is because sisters share all of their fathers' genes (since males are haploid and only contribute one set of genes) and, on average, half of their mothers' genes. This high degree of relatedness among sisters is thought to be a significant factor in the evolution of eusociality, where individuals live in cooperative colonies with a reproductive division of labor. In such societies, sterile or less-reproductive individuals (often females) may forgo their own reproduction to help raise their sisters, who are more genetically valuable to them. Conversely, a female is only related to her brothers by half the number of genes she shares with her sisters.