Biology Reference
In-Depth Information
development and as cytokines in the immune systems of insects (
Nassel 1993
).
Neuropeptides are being studied as an alternative to chemical pesticides.
However, neuropeptides offer a challenge because the insect cuticle contains a
lipid component that inhibits penetration of peptides and the gut, hemolymph,
and membranes of tissues contain peptidases that rapidly degrade peptides so
topical application or ingestion are not likely to be effective in delivering these
proteins (
Bendena 2010
).
11.4 Traditional Genetic Analyses of Behavior
Sometimes, as is demonstrated in examples below, mutations in a single gene or
a few major genes alter a behavior and the mode of inheritance can be assessed
by traditional methods. Traditional behavior-genetic analysis uses two main
experimental approaches:
crossing
and
selection
. A third, limited to
D. melano-
gaster
, involves analysis of
fate maps
in genetic mosaics to locate the anatomical
site of abnormalities that affect behavior (
Hotta and Benzer 1972
).
Many genes may influence an insect's behavior, although a specific behavior
sometimes can be altered by the mutation of a single gene (
Plomin 1990
). When
many genes are involved, analyses of behavior traditionally have required the
use of
quantitative genetic
methods and sophisticated statistical analysis.
11.4.1 Crossing Experiments
A crossing experiment involves mating individuals that differ in a particular kind
of behavior and then examining the behavior of their F
1
and backcross progeny.
(A backcross is a cross of F
1
individuals to a parental line, usually the homozy-
gous recessive one.) Ideally, the environment is controlled so that all individu-
als experience the same conditions. It is easiest to interpret the results of the
experiment
if
the individuals that are crossed differ
only
with regard to a single
behavioral attribute.
The phenotype of the F
1
and backcross progeny indicates whether a single
gene or multiple genes determine the behavior, and whether there is domi-
nance, sex linkage, or maternal influences. If many genes influence the trait, it
is difficult to determine the number of loci, their relationship to each other, or
their location on specific chromosomes because most insect species lack sufficient
genetic markers. New molecular and statistical methods using quantitative trait
loci (QTLs) may provide greater power to study and locate multiple and interacting
loci (
Doerge 2002
).
One aspect of honey bee behavior provides an example of a trait that appears
to be determined by a few genes. Other behaviors, including house-entering
