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Lecture 2

PSYCH 1XX3 Lecture Notes - Lecture 2: Allosome, Color Blindness, Egg Cell

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Joe Kim

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Development 2 2016-01-16
Intro to hereditary transmission:
Chromosomes and Genes:
Zygote: single cell with 46 chromosomes, 23 from each parents
oDivides at exponential rate
Any given couple can produce 64 trillion genetically distinct
Monozygotic: same sperm and ovum; genetically identical
Dizygotic: different sperm and ovum; share ~50% of genes
Sex chromosomes:
22 autosomes similar in male/females, 23rd one determines gender
ofemale: XX
omale: XY
genotype: an individuals inherited genes
phenotype: the expression of an individual’s genotype in terms of
observable characteristics
Genetic Expression:
Four patterns:
Simple dominant-recessive inheritance:
oA pattern of inheritance in which the expression of a trait is
determined by a single pair of alleles
oHomozygous: when two alleles have the same effect on the
oHeterozygous: when two alleles have a different effect on the
oDominant allele is expressed in the phenotype
oRecessive allele not expressed, but still heritable

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Polygenetic inheritance:
oMultiple genes are involved in the expression of a trait
oTwo dominant alleles are both fully and equally expressed to
produce a phenotype that is a compromise between the two
Sex-linked inheritance:
oGenes expressed on the X chromosome
oDisorder ex: colour blindness or haemophilia
oPhenotypic expression of the recessive alleles occurs less
frequently in females
oFemales rarely express sex-liked gene disorders, although
they are often genetic carriers
Intro to interactionist perspective
Extremist POV: nurture adapts the way a child grows up
Second extreme: genetics controlled how you were
Canalization principle:
genotype restricts the phenotype to a small number of possible
developmental outcomes
Some developmental processes are buffered against environmental
Ex: babbling, all kids babble the same way
Range-of-reaction principle:
Genotype establishes a range of possible responses to different
kinds of life experiences
Ex: height, need optimal environment and genes to be tall
Passive genotype/ environment correlations
The environment that parents choose to raise their children in was
influenced by the parents’ own genes
oEx: athletic vs. intellectual
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