PSYA01H3 Chapter Notes - Chapter 3: Homo Habilis, Axon Terminal, Human Genome Project

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Published on 26 Sep 2016
School
UTSC
Department
Psychology
Course
PSYA01H3
PSYA01
Chapter 3: Biological Psychology
3.1 Genetic and Evolutionary Perspectives on Behaviour
Our genetic code is not hidden in the darkest corners of our brains
oIt is found in the nucleus of most of the billions of cells in the human body
Genes: basic unit of heredity; responsible for guiding the process of creating the proteins that make up
our physical structures and regulate development and physiological processes throughout the lifespan
Genes are composed of segments of DNA
DNA (deoxyribonucleic acid): molec formed in double-helix that contains four nucleotides (ACGT)
Adenine, Cytosine, Guanine, Thymine
Genotype: genetic makeup of an organism--unique set of genes that comprise that individual’s genetic
code
Genes specify which types of molecules a cell should produce and when to produce them
Phenotype: physical traits/behavioural characteristics that show genetic variation (i.e. eye colour,
shape/size of facial features, and even personality)
This phenotype develops because of differences in the nucleotide sequencing of A, C, G and T, as
well as through interactions with the environment
The phenotype represents the physical and behavioural manifestation of that genotype that occurs
through interactions with the environment
Chromosomes: structures in the cellular nucleus that are lined with all of the genes an indiv inherits
Humans have approximately 20 000 – 25 000 genes distributed across 23 pairs of chromosomes
DNA is aligned along 23 paired chromosomes
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PSYA01
Chapter 3: Biological Psychology
oNumbers 1-22 are common to both males and females
oChromosome is sex linked, with males having the XY pattern and females the XX pattern
oTrisomy: when extra chromosome is present (most common chromosomal abnormality:
Down Syndrome on 21st chromosome)
Two corresponding genes
oHomozygous: if two corresponding genes at a given location on a pair of chromosomes
are the same
oHeterozygous: if two genes differ
Dominant gene from parent: upper case abbreviated nucleotide
Recessive gene from parent: lower case abbreviated nucleotide
The genotype represents what was inherited (ex. Tt, tt, TT)
The phenotype represents the physical and behavioural manifestation of that genotype that occurs
through interactions with the environment (ex. Being a taster or non-taster for the PTC sensation)
Behavioural Genomics: study of DNA and the ways in which specific genes are related to behaviour
Human Genome Project
oProject that resulted in the identification of approximately 20 000 – 25 000 genes
oDid not directly provide a solid understanding of any particular behaviour, but it has led
to an abundance of new techniques and information about where genes are located
Behavioural Genetics: study of how genes and the environment influence behaviour
Methods applied to humans typically involve comparing people to different levels of relatedness
(parents, offspring, siblings, unrelated individuals) and measuring resemblances for a specific
trait of interest
Monozygotic Twins: come from a single ovum, which makes then genetically identical (almost 100%
genetic similarity)
Dizygotic Twins (fraternal): come from two separate eggs fertilized by two different sperm cells that
share same womb; these have ~50% of their genetics in common
Longitudinal Studies: studies that follow the same individuals for many years, often decades (Ex.
A twin study to determine the influential role that genes play in depression in children and teens)
Heritability: statistic, expressed as a number between 0-1, that represents the degree to which genetic
differences between individuals contribute to individuals differences in a behaviour/trait found in a
population
0: genes do not contribute to individual differences in a trait
1: genes account for all individual differences in a trait
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PSYA01
Chapter 3: Biological Psychology
Heritability is affected by:
1. Amount of genetic variability within the group being studied
2. The variability in the environments that members of that group might be exposed to
For intelligence, heritability seems to increase with age (study on adopted children)
For depression, heritability seems to decrease with age
o0.76 at age 3
o0.48 at age 12
The fact that heritability estimates change over time based on our different experiences shows us
that nature and nurture interact to produce behaviour
oHowever they don’t tell us how that interaction occurs in our bodies and brains
Epigenetics: study of change in gene expression that occur as a result of experience and that do not alter
the genetic code
Gene expression is a life-long process
Factors such as diet, stress level, and sleep can influence whether genes are turned on or off
GR gene: found in the hippocampus; influences stress responses and can affect how well or how
poorly individuals respond to novel situations
Diathesis-stress Model: interaction between a genetic predisposition for a disorder and life stress
Natural Selection: process by which favourable traits become increasingly common in a population of
interbreeding individuals while traits that are unfavourable become less common
Because the adaptive or fit animals were more likely to survive and reproduce, these favourable
traits would then be more likely to be passed on to future generations (Evolution)
Evolution: change in the frequency of genes occurring in an interbreeding population over generations
Not a continuous process; if an animal is perfectly adapted for its environment, then there is no
evolutionary pressure for change to occur
Evolutionary psychology: attempts to explain human behaviour based on the beneficial functions
they may have served in our species' development
Intrasexual Selection: situation in which members of the same sex compete in order to win the
opportunity to mate with members of the opposite sex
Dominant male = alpha male
Evolutionary advantage: the animals most likely to become dominant are the most fit
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Document Summary

Our genetic code is not hidden in the darkest corners of our brains: it is found in the nucleus of most of the billions of cells in the human body. Genes: basic unit of heredity; responsible for guiding the process of creating the proteins that make up our physical structures and regulate development and physiological processes throughout the lifespan. Genes are composed of segments of dna. Dna (deoxyribonucleic acid): molec formed in double-helix that contains four nucleotides (acgt) Genotype: genetic makeup of an organism--unique set of genes that comprise that individual"s genetic code. Genes specify which types of molecules a cell should produce and when to produce them. Phenotype: physical traits/behavioural characteristics that show genetic variation (i. e. eye colour, shape/size of facial features, and even personality) This phenotype develops because of differences in the nucleotide sequencing of a, c, g and t, as well as through interactions with the environment.

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