PSYA01H3 Chapter Notes - Chapter 3: Lake Titicaca, Y Chromosome, Twin

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12 Aug 2016
Genes and behaviour
“Nature vs. nurture.” Do these twin influences grapple with each other for supremacy in
directing a person’s behavior?
This suggests that either genetics (“nature”) or the environment (“nurture”) played a major role
in producing particular behaviors, personality traits, psychological disorders, or pretty much any
other thing that a human does
Both nature and nurture play a role in directing behavior
It is the interaction of genes and environmental influences that determines what humans do
What are Genes?
Gene Unit of hereditary transmission
oSections on a strand of DNA (deoxyribonucleic acid)
oOrganized into large threads called chromosomes
oChromosomes Strands of DNA wound around each other in a double-helix
Chromosomes come in pairs, and humans have 23 pairs each
These pairs of chromosomes are similar but not identical: You inherit one of
each pair from your father and one from your mother
There’s a twist, however: The selection of which of each pair is given to you is
Chromosomes contain DNA and DNA contains genes OR chromosomes are composed of DNA
and DNA is composed of genes (which are sections of DNA)
Figure 3.25 Genes, Chromosomes, and Their Recombination
Most striking example of this random distribution is the determination of sex
Sex-determining chromosomes: X and Y chromosomes;
oFemales have two X chromosomes
oMales have one X and one Y chromosome
oYou inherited an X chromosome from your mother since she has only X chromosomes to
oYour biological sex, therefore, was determined by whether you received an additional X
chromosome or a Y chromosome from your father
There is considerable variability in the genes that individual offspring receive
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