Sex determination within the honey bee

In honeybees, sex is determined by the fertilisation or non-fertilization of eggs, rather than the presence or absence of sex chromosomes on the chromosomes (or honey bees). It was a Catholic priest named Johann Dzierzon who made the first discovery of this method of sex determination, back in 1845. According to Dzierzon, only male progeny are produced by a virgin queen who has not taken a mating flight (queens only mate when they are in free flight away from the nest)  His report, which was published more than 50 years before the discovery of sex chromosomes, was the first comprehensive description of a sex determination system . We now know that honey bees are not the only animals that reproduce using a haplodiploid mode of reproduction, with approximately 20% of animal species using this mode of reproduction. In haplodiploid systems, male progeny develops normally from unfertilized eggs, which are haploid and contain only one set of chromosomes. In haploid systems, male progeny develops abnormally. It is from fertilised honey bee eggs, which are diploid and contain two sets of chromosomes, that queens and worker bees are produced.

It took the researchers by surprise to discover diploid male honey bees with Complementary Sex Determination chromosomes in inbreeding studies with honey bees. The presence of these diploid males suggested that neither the process of fertilisation nor the haploid or diploid state of the egg is the primary signal for sex determination in honey bees, as previously thought. Because the appearance of diploid males was associated with inbreeding, researchers proposed the complementary sex determination hypothesis, according to which the sexual fate of a single sex determination locus (SDL) is determined by a single gene . According to this hypothesis, fertilised eggs that are homozygous at SDL develop into diploid males, whereas fertilised eggs that are heterozygous at SDL develop into females. The unfertilized, haploid eggs of the queen, which must be hemizygous at the SDL in order to produce fertile males, are used to produce fertile males . Because of homozygosity at the SDL, males die. When the diploid males hatch from their eggs, worker bees prey on them. This results in a typical brood pattern in honey bee colonies, which is referred to as shoot brood by beekeepers .

After the sex determination locus in honey bees was discovered, the complementary sex determiner (csd) gene was discovered and named after it . Csd is a protein that is encoded by the csd gene and has at least 15 allelic variants, with each variant differing by an average of about 3 percent of their amino acid residues  csd gene product is required for female development due to the fact that the loss of the csd gene product results in the complete conversion of female embryos to males when the csd gene product is deficient . In recent years, the feminizer (fem) gene has been identified as a potential target of the csd gene product .Because the fem transcript splices differently in males and females, only female cells are capable of producing a functional fem gene product. In males, splicing alters the coding sequence of the fem gene by inserting a stop codon.

The Concept of Complementary Sex Determination Has Changed

Bees, wasps, and ants are among the hymenopteran species that employ the complementary mode of sex determination. However, csd gene products are not required for the determination of sexual orientation in every species that uses the complementary mode. According to gene orthologs in other bee and wasp species, the csd gene was recently created by gene duplication within the honey bee lineage from a copy of the ancestral progenitor gene feminizer (fem). The csd gene is a member of the csd gene family . The fem gene has remained a conserved component of insect sex determination pathways throughout the evolutionary history of the species. During the evolution of honey bees, the fem gene has been identified as a potential target of csd activity . The most likely explanation for how the csd gene came to have its current function is adaptive evolution. The duplication of the ancestral sex-determining fem gene, followed by positive selection in one of the duplicates, favouring the presence of a new upstream signal, eventually resulted in the development of the honey bee’s novel sex determination system , according to one theory . Simple molecular changes in the existing genetic repertoire can result in the evolution of new sex determination systems, as demonstrated by the evolution of the csd gene. According to Charlesworth  (2005), the reduced meiotic recombination at the sex determination locus observed in the honey bee lineage may also indicate that the csd gene will gradually degenerate over time, thereby facilitating the evolution and positive selection of alternative sex determination signals over long evolutionary time scales.

Honeybees use a haplodiploid sex determination method to determine their gender. Men develop from unfertilized eggs as haploids, while females develop from fertilised eggs as diploids. Males are more common than females. It was a Catholic priest named Johann Dzierzon who made the first discovery of this method of sex determination, back in 1845.

In honeybees, sex is determined by the fertilisation or non-fertilization of the eggs, rather than the presence or absence of sex chromosomes on the chromosomes. Honeybee male progeny develops normally from unfertilized eggs, which are haploid and contain only one set of chromosomes, in the same way that female progeny does. It is from fertilised honey bee eggs, which are diploid and contain two sets of chromosomes, that queens and worker bees are produced.

CONCLUSION:

We can conclude that the number of chromosomes received by bees has an impact on their ability to determine their gender. Bees have 16 chromosomes in total, and drone bees have 16. A queen bee has 16 chromosomes in total, and a drone bee does not have 16 chromosomes in total (32).

The sex-determination system used by a bee is not well understood.