Lesson 84: Honey Bee Genetics Basics

Genes, traits, and the unusual family life of honey bees, and what it means for choosing and breeding queens

When you choose a queen, you're choosing genes for your whole colony: how gentle it is, how much honey it makes, how well it resists mites and disease. A little genetics helps you understand why colonies differ so much, and why breeding bees is harder than breeding most animals.

Genes, genotype and phenotype

• DNA is the blueprint for building an organism. A gene is a stretch of DNA that tells the cell how to make a protein. Proteins build cells and control how they work.
• A gene can come in different versions, called alleles. Different alleles can make slightly different proteins, which can produce different traits.
• An individual's genotype is its genetic makeup. The traits you can see or measure are its phenotype: in bees, things like body color, pollen-hoarding behavior, or resistance to chalkbrood.

Honey bee families are unusual

1. Females have two sets of genes; males have one. - Queens and workers develop from fertilized eggs: they get one set of genes from the queen (mother) and one from a drone (father). - Drones develop from unfertilized eggs (lesson 6): they have only one set of genes, all from their mother. A drone has no father, and all the sperm he makes carries the same genes.

2. The queen mates with many drones. On her mating flights (lesson 13) she mates with a dozen or more drones and stores their sperm for life. So a colony is really many groups of half-sisters: workers with the same father are very closely related, while workers with different fathers share only their mother's genes. This is part of why colonies can show a mix of behaviors, and why a colony's traits come partly from drones you never chose.

What this means for you: you choose the queen's mother, but not the fathers. The drones she mates with come from colonies all around your area, including your own and your neighbors' hives. That's why flooding an area with good drones (keeping drone-rich colonies of good stock) helps a breeding program (lesson 83), and why queens mated in areas with Africanized bees may carry Africanized traits (lesson 16).

Simple and complex traits

Some traits come from a single gene. For example, "cordovan" color (a brown instead of black body) is a recessive trait on one gene: - a female shows it only if she gets two copies (one from each parent); - a drone shows it with just one copy, since he has only one set of genes.

Most traits are far more complex, controlled by many genes. Hygienic behavior, for example, involves at least two and possibly up to nine genes. Traits like gentleness, honey production and mite resistance are similar.

Environment matters too

Genes aren't the whole story. The environment changes how genes are expressed: - Queens and workers start from the same kind of egg. Whether a female larva becomes a queen or a worker depends on the diet she's fed (lessons 7, 79). - Winter bees (long-lived bees that carry the colony through winter; lesson 14) develop in response to fall signals such as cooler weather, shorter days and less incoming food. - Mite-resistance behaviors can rise or fall with strong nectar flows or dearths.

So judge colonies fairly: compare colonies at the same time of year, and choose breeding stock that shows good traits over more than one season.

What to remember

• Genotype = genes; phenotype = traits you see. Alleles are versions of a gene.
• Workers and queens get genes from mother and father; drones only from their mother.
• The queen mates with many drones, so a colony is many half-sister families, and you don't control the fathers.
• Some traits are single-gene (cordovan color); most are many-gene (hygienic behavior).
• Environment affects traits, so compare colonies at the same time and over more than one season.

Quick check

1. Why does a drone show the cordovan color with just one copy of the gene?
2. Why do workers in one colony often behave differently from one another?
3. Why should you judge a possible breeder colony over more than one season?

Adapted from: Penn State Extension, Honey Bees: From Genotype to Phenotype (Underwood, Anton & Grozinger); Penn State Extension, An Introduction to Queen Honey Bee Development; UF/IFAS Extension, Using Nucs in Beekeeping Operations (IN869); Delaplane, Honey Bees and Beekeeping (UGA Bulletin 1045, rev. 2017).

Adapted from university Extension sources. Experienced Georgia beekeepers are reviewing these lessons. See something that doesn't match your experience? Tell us.