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Lecture 3

PSYC 3100 Lecture Notes - Lecture 3: Phenotype, Horizontal Transmission, Bird Vocalization


Department
Psychology
Course Code
PSYC 3100
Professor
Pat Barclay
Lecture
3

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Thursday, September 13th, 2018
Evolutionary Psychology
Lecture 3 - Genes, Development & Behaviour & Why Nature and Nurture Won’t
Go Away
Last class we defined what a genotype and a phenotype was
The question we want to talk about today is how do we get from a genotype
to a phenotype?
Process of Phenotypic Development
Phenotype = Gene + Environment (this interaction is Development)
o Genes act as a part of the developmental path
o Genes and environment have statistical effect
o Genes don’t change but the expression does change
Different genes can be turned on and off and this how many
genes have their effect
o Genes require some kind of environment to act because something
needs to trigger it to be transcribed
o The environment requires genes to act on
Without genes nothing is being transcribed, nothing is getting
done
An organisms that has no genes is not responding
o Its only the genotype that gets passed on genetically
The consequences of that genotype is what decides to get
passed on to the next generation
Intro to DNA transcription
o Transcription the process of reading a making a copy of DNA; RNA
o Transcription is going on constantly and this now you do various
things like learning and stuff like that
o Some genes are only turned on periodically throughout your life
o For the RNA to do anything it needs to be transcribed
o Nature in a sense needs nurture for that gene to do something
o The way that the environment determines which genes gets turned on
and off
o Example rock…there is not genes to be activated and it cannot
respond it any meaningful way
o What we want to know is which genes are being turned on and off
Behavioural Phenotype: a) Gene + Environment causes brain development;
b) brain + Environment produce internal response; c) response causes
observable behaviour; d) consequences + brain cause learning (change in
brain for next time period)
o The environment acts on the brain and triggers a response (an
emotion)
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o Example you smell cookies, that smell goes into your brain and that
triggers hunger, and the phenotype (eating the cookie)
Why genes and environment need each other
Example of gene-environment interactions
Temperature-dependent sex determination (most turtles)
o In humans our biological sex is determined by our genes
XX female
XY male
o This is not the way it is in all organisms
o Birds
ZZ male
ZW female
o Reptiles and turtles
Their sex is determined by the temperature of the egg
In some systems eggs in high temperature will develop into
females and low temperature will develop into males. In other
systems it will be reversed
Temperature is triggering gene expression which causes
hormone production which then triggers sexual differentiation
The temperature is turning on and off genes
o With humans the temperature doesn’t matter, that’s not how humans
sex can be differentiated
o Because males and females act differently in this species, their
behaviour is different too and these are all triggered by the
temperature of the egg
Humans: SRY gene and social reactions
o There is not a lot of the Y chromosome in the male chromosome, but
one thing that is on the Y chromosome is the SRY
o This SRY turns on a lot of genes that have to do with males and which
masculinises the egg
o In humans, people tend to treat males and females differently
o People who have the SRY gene get treated like a male
o People who don’t have this SRY gene get treated like a female
o You can argue that this one gene causes the many differences we see
in humans
o This gene is setting a person up for a particular environment and then
the environment changes what the person does because it causes
them to be exposed to an environment that a boy or a girl is exposed
too…different environments
o They are treated differently because they either look like girl or they
look like boy
o To say its nature or nurture doesn’t really make sense
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