Why do male bees have no father?

Let us get straight to the point: bee genetics is genuinely strange.

Most of us have heard about the importance of genes, about how a mother and a father each contribute their own part, and so on. We take it for granted that the mother contributes chromosomes from her egg and the father from his sperm. A large part of the animal kingdom works on exactly these principles.

But that is not the case with honey bees. They use a completely different approach to passing chromosomes on, and it has a few strange consequences. Here are some facts about the male bee, the drone:

• They have no father.

• They have a grandfather.

• They can be fathers to daughters, to granddaughters and to grandsons.

• They cannot have sons.

Confused? Keep reading.

Diploid and haploid

The reason for all this strangeness is a sex determination system called haplodiploidy. In high school biology we were taught that every egg is fertilized and that offspring result, female or male. That, for example, is how it works in humans.

But in the strange world of the honey bee, a male develops from an unfertilized egg: an egg laid by a queen without being fertilized by sperm. The male bee is called haploid. Reproduction from unfertilized eggs is called parthenogenesis.

The more familiar situation, where the queen fertilizes an egg with sperm, produces a female bee. That means the egg is destined to become a worker or a queen. Female honey bees are diploid.

The effect on genes

So what does all this mean for passing genes across generations? Let us take humans as our baseline.

Our genes sit on chromosomes. We receive 46 chromosomes, 23 from our mother and 23 from our father. Passing genes down through the generations means that the traits of both sides of the family show up in us and are expressed by things like eye color, height and so on. All of this is because we come from an egg contributed by our mother and sperm contributed by our father.

Honey bees follow the same basic principle, but only the females.

Female bees develop when a queen lays an egg that she fertilizes. Even though the numbers differ in bees compared with humans, each side of the family contributes the same number of chromosomes (16).

It gets a little stranger when we turn to the haploid, that is, the drone. Male bees carry only the chromosomes from the egg, because they were never fertilized. So drones have just 16 chromosomes, all of them from the queen.

Want to see it in a video? Recommended watching: Why Don't Bees Celebrate Father's Day? by Scientific American.