PSYCH 2TT3 Chapter Notes - Chapter 4: Eocene, Manganese, Habituation

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23 Dec 2014
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Molecular genetics and development:
Bee colonies and queen reproduction
Colonies have millions of workers that do not produce offspring even though they are physiologically capable of doing
so. Only the queens reproduce.
What is the molecular genetics factor that prevents the workers from reproducing?
When queen dies, workers get aggressive and finally one wins the fight and becomes the queen.
The queen sends chemical signals that don’t allow workers to reproduce. When that signals stops, it causes the start of
aggressive behaviour.
The gene neofem2 seems to be responsible for this
phenomenon, which in termites appears to be involved
in the production of chemical signals called pheromones
that the queen produces.
Experimenters quit the neofem2 gene in queens, it did
not affect the behaviour of the queens but it dramatically
affected the behaviour of the workers making them more
aggressive towards each other.
Developmental pathway in termites is affected by the
presence or absence of a particular gene in the queen of
the colony.
Molecular genetics and animal behaviour:
we will look at two other important ways that behavioral
genetics contributes to the study of ethology:
1. Using Mendels laws of genetics to predict the distribution of behavioral phenotypes.
2. Using quantitative trait loci (QTL) analysis to map the location of clusters of genes linked to behavioral traits.
Mendels law:
Mendel’s first lawthe principle of segregation—states that individuals have two copies of each gene, that such
genes remain distinct entities, and that these genes segregate during the formation of eggs or sperm.
Mendel’s second law—the law of independent assortment—states that whichever allele is passed down to the next
generation at one locus is independent of which allele is passed down at other loci. Today, we know this second law is
true only for what are called unlinked loci. (allele for one trait is independent of allele for another trait)
Dominant and recessive allele. The dominant allele masks the effect of the recessive allele.
Example: Independent males, which make up the majority of individuals in most populations, guard small mating
territories. “Satellite males,” in contrast, temporarily share an independent males mating arena and form a kind of
alliance with independents, in which both individuals court simultaneously to attract the attention of females.
Independent and satellite—are primarily controlled by a single gene with two alleles labelled S and s. The S allele is
dominant and codes for satellite male behaviour, whereas the s allele is recessive and two copies of this allele are
necessary for the development of an independent male. As such, SS and Ss males are satellites, and ss males are
independents.
Locating genes for polygenic traits:
Traits associated with variation at more than one locus are called polygenic traits
Many genes coding for one trait.
For polygenic behavioral traits, behavioral geneticists often search for a set of genes, each of which contributes a small
amount to the expression of the trait of interest.
When researchers conduct such searches, they are looking for what are called quantitative trait loci (QTL’s)
QTL mapping is a powerful way of finding at least the general region of the genome in which quantitative trait loci
reside.
Mapping steps:
1. Step 1. We typically begin the process by selecting two parental strains that (1) differ considerably in their values of the
quantitative trait and (2) differ at a set of marker alleles. Parental strain 1 has a lower distribution of trait values than
does strain 2; strain 1 is homozygous for the A, B, and C marker alleles, while strain 2 is homozygous for the a, b, and
c marker alleles.
2. Step 2. The next step is to cross these two strains to produce a set of progeny. This new generation is referred to as the
F1 generation. If the parents are homozygous at the marker loci, these F1 progeny will be heterozygous at each marker
locus, and typically they will manifest intermediate values of the quantitative trait.
3. Step 3. The F1 individuals are then mated to produce an F2 generation. For the F2 individuals, we measure (1) the
genotypes at the marker loci, and (2) the value of the quantitative trait. From this information, we can infer which
marker loci are most closely associated with QTLs for the behavioral trait in questions.
Honey bee foraging and mRNA
they examined how levels of per messenger RNA (mRNA)—a single-stranded RNA that is critical for protein synthesis
—might influence the developmental changes associated with the transition to forager
Precocious foragers had per
mRNA levels that did not
differ from those of typical
(older) foragers, suggesting a
link between per mRNA and
foraging, as opposed to a more
general connection between
per mRNA and development.
Proximate link between mvl
and foraging can be found in
the fact that when bees were
experimentally treated with
manganese, their response to
sucrose increased, and they
made the transition from nurse
to forager at an early age.
This means that the amount of
per mRNA doesn’t depend on
age, it depends on the foraging behaviour. “needs of the colony”
Ultra Violet Vision in Birds:
Zebra finch can see ultra violet, but they changed an amino acid, now can see
violet light and not ultra violet anymore.
In chickens they can’t see ultra violet light, can see violet, changed one amino
acid made them see ultra violet light.
This shows that vision can change just due to simple events like mutations and
become advantageous and stay in a populations.
Song acquisition in birds:
expression of the FOXP2 gene in brain regions is
associated with both song perception in birds and
language acquisition in humans
When this gene is knocked out, ability to learn
song from adult bird is very difficult.
They found that mRNA levels associated with a
gene called zenk increased after the birds heard
zebra finch songs, and that increase was
associated with an increase in the number of
neurons in the neostriatum
When another species song, this mRNA did not
increase and when they didn’t hear any song,
again the levels of the mRNA didn’t increase.