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Genetics and Behavior
With reference to relevant research
studies, to what extent does genetic
inheritance influence behavior?
Like many other animals humans have sex
• Conception begins with
the drop of an egg and
the release of about
200 million sperm.
• The sperm seeks out
the egg and attempts to
penetrate the eggs
surface.
Once the sperm
penetrates the eggwe have a fertilized
egg called……..
• A zygote
Zygote
• Less than half of all
zygotes survive first
two weeks.
• About 10 days after
conception, the zygote
will attach itself to
the uterine wall.
• The outer part of the
zygote becomes the
placenta (which filters
nutrients).
After two weeks the zygote becomes
a…
Embryo
• Lasts about 6 weeks.
• Heart begins to beat and
the organs begin to
develop.
By nine weeks we have a…
Fetus
• By about the 6th month, the
stomach and other organs
have formed enough to
survive outside of mother.
Then we have childbirth….
But why go through all that trouble?
Wouldn’t it be easier if people
could just copy themselves
instead of going through all
these messy stages?
• Watson and Crick in 1953
discovered the DNA
molecule.
• SEX and the birthing
process brings together the
genetic information from to
parents in a fertilized egg.
• GENETIC DIVERSITY
Chromosome Breakdown
Chromosomes
Genes
DNA
Nucleotides
Genetic Similarities
Mr. D is
98%
99.9%
99.9%
Gene Mapping
• Some scientists are
trying to determine the
effect of a particular
gene on behavior such
as temperaments or
psychological disorders.
Caspi et al. (2003)
The role of the 5-TT gene in depression after stressful events.
• Longitudinal Study (vs
Cross Sectional)
• The 5-TT gene
influences the level of
serotonin, which is
known to play a role in
mood.
Caspi et al. (2003)
The role of the 5-TT gene in depression after stressful events.
• There are two types of 5HTT genes.
• Long- a little over 50% of
population
• Short- a little less than
50%
• The researchers
compared participants
with normal 5-HTT (long)
genes with shorter alleles.
• Specifically after stressful
events.
Caspi et al. (2003)
The role of the 5-TT gene in depression after stressful events.
Results
• After stressful events,
the participants with
the shorter 5-TT gene
were more likely to
become depressed.
• The 5-TT gene could
indicate vulnerability to
depression.
Caspi et al. (2003)
The role of the 5-TT gene in depression after stressful events.
Evaluation
• Since so many people
carry it (almost half the
population), it is hard to
say that in is the gene
that made the difference.
• Maybe it was the
environmental factors
(stressful events) that
caused the depression.
• Did not show a causeeffect relationship.
Chromosomal Abnormalities
• Gender comes from
23rd pair of
chromosomes…men
have XY…woman have
XX.
• Turner’s syndrome is
single X.
• Klinefelter’s syndrome
is extra X…XXY
• XYY- Super male