Biology Reference
In-Depth Information
behavior in the mosquito
Aedes aegypti
, foraging in
D. melanogaster
, and host
choice in the parasitoid
Nasonia
also appear to be determined by one or a few
genes.
11.4.1.1 Susceptibility to American Foulbrood in
Apis mellifera
Susceptibility to foulbrood disease, caused by
Bacillus larvae
, originally was ana-
lyzed by crossing two inbred
A. mellifera
strains with differing levels of resis-
tance (
Table 11.1
). The differences in resistance were attributed to differences
in “hygienic behavior” in worker (sterile female) bees and represent one of
the first demonstrations that behavior is genetically determined (
Rothenbuhler
1964
). Resistant workers (
=
hygienic) consistently remove dead larvae and pupae
from the brood nest at a high rate, thus slowing the spread of the bacteria
through the colony by reducing contamination. Crosses between “hygienic”
queens and susceptible “nonhygienic” haploid males yield F
1
worker prog-
eny that are nonhygienic, indicating that the “genes” conferring resistance are
recessive.
Progeny produced by backcrosses to the homozygous-recessive hygienic
strain yielded approximately 25% hygienic workers, which is consistent with
the hypothesis that hygienic behavior is determined by two recessive loci
(
Table 11.1
). Under a two-locus model, hygienic worker queens are homozy-
gous for two genes,
uu
and
rr
. The hygienic workers (
uu
,
rr
) both
u
ncap the
cells (
uu
) containing dead brood
and
r
emove them (
rr
). However,
uu
,
r
+
r
indi-
viduals will uncap the cells, but not remove dead brood. The
u
+
u
,
rr
individuals
do not uncap brood, but will remove them if the cells are uncapped for them.
Individuals that are
u
+
u
,
r
+
r
are unhygienic, and will neither uncap nor remove
Table 11.1: Crossing Experiment to Explain Differences in Nest-Cleaning Behavior Among
Inbred Lines, F
1
and Backcross Progeny of the Haplo-Diploid Honey Bee
Apis mellifera
Supports the Two-Locus, Two-Allele Model.
Parental lines
Hygienic (diploid)
uu
,
rr
queen
X
Unhygienic
u
+
,
r
+
(haploid) male
F
1
progeny
All diploid sterile
workers
u
+
u
,
r
+
r
(Unhygienic workers)
Ratio of backcross progeny (workers)
Cross of
u
+
u
,
r
+
r
1:
1:
1:
1:
queen X
uu
,
rr
uu
,
r
+
r
u
+
u
,
rr
u
+
u
,
r
+
r
hygienic
u
,
r
male
Hygienic
Uncaps, doesn't
remove
Removes, doesn't uncap
Unhygienic
Data from Rothenbuhler (1964).
