Principles of Honeybee Genetics

Use this page as a tool for visualizing and understanding some of the various genetic mechanisms at work in honeybees.

• Mating behavior - multiple mates make for a complex family.
• Chromosome number - key in understanding bee genetics.
• Cordovan color- a useful genetic marker, controlled by a recessive gene.
• Hygienic behavior: two recessive genes for uncapping and removing diseased brood.
• Tracheal mite resistance - thought to be controlled by dominant gene(s).
• Sex alleles - determines solid or scattered brood pattern.
• Mitochondrial DNA - used to trace the maternal lineage of bees.
• Oddball bees - a gallery of unusual bees.
• Principles of honey bee genetics - adapted from an EAS workshop

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Mating behavior

The queen mates in flight at one week old. She my fly more than a kilometer seeking multiple mates. After one or more mating flights, she never mates again. Sperm are stored in the spermatheca of the queen for life.

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To keep things simple, further examples will show a queen mated to a single drone.

This can be done with instrumental insemination, to sort genetic traits.

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Number of chromosomes in bees. A key factor.

• Drones result from unfertilized eggs (parthenogenesis).They have no father.
• All eggs and sperm carry 16 chromosomes each.
• Each egg contains a unique combination of 50% of the queens genes.
• All 10 million sperm produced by a drone are identical clones.
• Since each queen mates with 10-20 drones, colonies are comprised of subfamilies, each having the same mother but different fathers.
• Workers of the same subfamily are related by 75% of their genes.
• This "extra" close relatedness may explain the cooperative, and altruistic behaviors found in colonies.
• It also explains why workers forego their own reproduction in favor of helping their queen mother raise more sisters. Their sisters are more closely related to them than their own offspring would be. (75% vs 50%)

Queens and workers are both females. Their differences arise from how they were fed while developing as larva. A worker has the same genes as she would have, had she been raised a queen. Egg laying workers appear in queenless colonies.

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Cordovan color

Cordovan Italian

Wild type Italian

Why is cordovan coloration useful? 1) Cordovan Italian queens are easier to find in a hive. 2) The presence of only cordovan drones in a hive confirms the presence of a cordovan queen. 3) Mating control can be assessed by estimating the percentage of cordovan workers in a hive.

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Hygienic behavior

Hygienic behavior is expressed by bees uncapping and removing diseased brood. Recessive genes are expressed only if the dominant version is absent. Bees carrying a recessive gene can pass it on without expressing the trait. A gene can become "fixed" in a population when other versions are eliminated.

Recent research suggests that this model of hygienic behavior may be too simplistic. Evidence now shows that there may be as many seven genes involved.

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Tracheal mite resistance

Resistance appears to be controlled by dominant gene(s). Only one dominant allele is necessary for expression of resistance. The mechanism of resistance is not known for certain. There is evidence that grooming behavior is involved.

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Sex alleles

Why is some brood not viable? If a fertilized egg has two of the same sex alleles, it is not viable. The result is an abnormal drone (diploid drone) which never matures. These diploid drone larva are eaten by workers as the egg hatches. Brood pattern and viability are determined by the diversity of the sex alleles. In bee breeding, the goal is to maintain a diversity of sex alleles while selecting for other desirable characteristics. Inbreeding results in a reduction of alleles with up to 50% non viable brood.

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Mitochondrial DNA

Mitochondrial DNA is passed on only through the females. It is not contained in the nucleus of cells and therefore does not participate in sexual reproduction. It changes very slowly, only by mutation. It's used to trace maternal lineage.