(Editor's note; In readings regarding our dear bees, wasps and ants
we have again and again run into expressions like 'inclusive fit-
ness, 'kin selection', 'haplodiploidy' 'altruism' and a few other terms,
not knowing what really meant. This article clears up a lot of
questions. By the way, don't let the title make you think, this isn't
for you, I'm only interested in Bumblebees and hornets. The title
should have been in my opinion "Hymenopteran Genetics, Part I")
In this article we take a look at basic, hopefully easy to read and
understand honey bee genetics. In the course of the reading it
should become obvious to you why bees have arranged things the
way they have. The big thing about bees is that drone bees come
from an unfertilised egg and this one fact makes bee genetics very
different and as long as you remember this, the rest of bee genetics
becomes easier to understand.
Chromosomes contain the genes that make us up. Humans have two
sets of chromosomes, 46 chromosomes in total. 23 from the female
egg and 23 from the male sperm. Queens and worker bees have
32 chromosomes, again two sets, 16 from the queens egg and 16
from the drone's sperm. They are diploid. Di means two (sets)
and ploid means chromosome. Drones which result from an unfer-
tilised egg have 16 chromosomes only because they receive only
the 16 chromosomes from the queen's egg. They are called haploid.
one (set) chromosome. When a queen mates with a drone she will produce eggs. As in humans and most other animals, each egg
will contain half her total chromosomes, in the case of a bee this
is 16. This means that like a human mother she can only ever pass
on to her offspring 50% of her genes. This egg will contain a
random selection of her genes.
The drone will contribute the other 16 chromosomes, BUT which
are 100% of his total genes. A resulting worker or queen therefore
will receive 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 therefore have a 75% relationship. These sisters are called
supersisters and comprise definite groupings within a hive. In
humans and other animals your offspring will have only a 50%
relationship. 50% from the mother's genes and 50% from the
father's genes. If a worker had her own offspring, she too would
only have this 50% relationship with her offspring. By helping the
queen raise her supersisters she has raised this relationship to 75%.
There is a principle in biology that an organism will tend to do
whatever most efficiently gets more of its genes into the next
generation and by operating in this fashion, bees have worked out
a very efficient system for doing this. Honeybee queens will mate
will many drones. The reason for this is probably to gather up a wide genetic diversity for the colony and to reduce the possibility of
inbreeding. This means that there can be many different families
of supersisters in the hive, each with the same mother but a
different father. A worker in the same family will have a relation-
ship to a sister of 75% and to a sister of the same mother but a
different father of 25%. This difference in relationship has many
effects on the life and work of the colony and we will look at this and other aspects in future articles.
A final word; multiple matings in honeybees is a great exception
in hymenoptera as a whole.
Source: Apis-UK, July 2005, abridged.