Download Chapter Two: Biological Foundations - PSYC DWEEB

Genetic Inheritance
Conception
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The union of sperm and ovum create a zygote
The zygote contains a complete set of 46 chromosomes
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The first 22 pairs are called autosomes.
The 23rd pair are the sex chromosomes.
DNA
Genes
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Genetic Principles
Genes
 Genotype.
 Phenotype
Reaction range
Alleles
 Homozygous Alleles (similar)
 Heterozygous Alleles (different)
 dominant - recessive gene principle
 incomplete dominance (blending)
 codominance (type AB blood)
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Genetic Inheritance
Single Gene-Pair Inheritance
Polygenetic Inheritance
Genetic Imprinting
 Genes are (chemically marked) in one of the parents and have different
effects depending on which parent carries it.
 Huntington disease manifests earlier if passed on by the male
 Asthma / females , Diabetes / males
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Genetic Inheritance
Sex Linked Genes or Traits (X-linked inheritance)
 ex: hemophilia, red/green color blindness
Mutations
 A sudden, permanent alteration in DNA
 occurs spontaneously or by environmental hazards
Chromosomal Abnormalities
 Often the result of the 46 chromosomes not being divided equally (too
many or too few)
 Down Syndrome
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Genetics & Environment
Heritability:
The amount of variability in a population
on some trait dimension that is attributable
to genetic differences among those
individuals
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Gene-Environment Relationships
Epigenetic View: Heredity  Environment
 Passive Gene-Environment Relation
 Evocative Gene-Environment Relation
 Active Gene-Environment Relation
 Shared and Non-shared Experiences
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Germinal Stage (Weeks 1-2)
The zygote, begins to divide, and travels down the fallopian tube.
The new cells form the blastocyst, which attaches itself to the uterine
wall
 The blastocyst forms several layers of cells
 The outer cells (trophoblast) form the placenta.
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Embryonic Stage (weeks 3 – 8)
The inner cells of the blastocyst which will become the embryo differentiate
into three layers:
 Ectoderm: Outermost layer which will
become skin, hair, nails, the nervous
system, and sensory receptors
 Mesoderm: Middle layer which will
develop into the circulatory system,
bones, muscles, excretory and
reproductive system
 Endoderm: Undermost layer which will develop into
the digestive and respiratory systems
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Embryonic Stage (weeks 3 – 8)
The formation of organs begins (organogenesis)
Sexual differentiation takes place around the 7th or 8th week
By the end of the embryonic stage about 95% of body parts and systems have
begun development.
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Fetal Stage (Week 9-Birth)
This period involves the dramatic increase in body
size and completion of all physical structures
Age of viability = approx. week 25
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Prenatal Growth
Occurs in three patterns:
 Orthogenic
 Cells are all the same and then differentiate
 Cephalocaudal:
 Latin for “from head to tail”.
 Proximodistal:
 Latin for “from near to far”.
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Influences on Prenatal
Development
Nutrition
Stress
Mother’s Emotional state
Mother’s Age
 Nearly 50% of pregnancies among women in their 40’s and 50’s
result in miscarriage.
Father
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Influences on Prenatal Development
Teratogans are any disease, drugs, or other environmental agents that can
cause damage to a developing fetus.
Effects depend on:
 Dose
 Heredity
 Presence of other teratogens
 Age of child
 Sensitive period
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Postnatal (Postpartum) Depression
Occurs in 1/10 new mothers
Effects bonding and initial care of child
Effects on mother
 May not want child
 Mood lability and other symptoms of depression
 Psychosis
 SI / HI
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Postnatal (Postpartum) Depression
Effects on child
Susceptibility
 Past episode(s) of post partum (30 to 50% chance with each subsequent
delivery)
 Personal past history of a mood disorder
 Family history of Bipolar disorder (even if not personally experienced)
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