Agriculture Reference
In-Depth Information
Understanding basic bee genetics
Passing on genes
Chromosomes contain the genes that determine an organism's make-up. Humans have
two sets of chromosomes, 23 from the female egg and 23 from the male sperm, which
makes 46 in total. Queen and worker bees have 32 chromosomes, again in two sets
- 16 from the queen's egg and 16 from the drone's sperm. Queen and worker bees are
therefore
diploid
:
di
(two sets) and
ploid
(of chromosomes). Drones, which result from
an unfertilized egg, have 16 chromosomes only. They receive these from the queen's
egg (they have no father). They are therefore called
haploid: ha
(one set) and
ploid
(of
chromosomes).
After a queen has mated with a drone, she will produce eggs. As in humans and most
other animals, each egg will contain half her total chromosomes - in this case, 16. This
means that she can pass on to her offspring only 50% of her genes, and her eggs will
contain a random selection of these genes.
The drone contributes the other 16 chromosomes, which are 100% of his total genes.
Each sperm from a drone is therefore identical - i.e. it is a clone. A worker or queen
thus receives 50% of her mother's genes and 100% of her father's genes. A sister worker
or queen from the same drone and queen will hence have a 75% relationship. These
sisters are called super-sisters and comprise definite groupings within a hive.
In humans and other animals, the offspring have only a 50% relationship (50% from
the mother and 50% from the father). If a worker had her own offspring, she, too,
would have only this 50% relationship with her offspring. By helping the queen to
raise her super-sisters, however, she has increased this relationship to 75%. This close
relationship probably explains why workers have given up reproducing in favour of
helping the queen raise more super-sisters. This may satisfy a biological principle
whereby organisms try to pass on to the next generation as many of their genes as
possible. This is the first complication for bee breeders.
