Genetics & Prenatal Development

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Genetics Prenatal Development

• 2/13/07

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Prenatal Influences on Development

• Both genetic and environmental factors influence
  prenatal development
• Emphasis on how biological factors affect social,
  emotional and cognitive development rather than
  physical development itself

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Genetics

• Genotype refers to the genetic information that
  determines inherited characteristics
• Phenotype refers to directly observable
  characteristics
• more than one genotype can result in the same
  phenotype
• Chromosomes are made up of DNA
• 23 sets
• 22 pairs of autosomes
• 1 pair of sex chromosomes (XX or XY)

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Mechanisms of Inheritance

• Polygenic
• Single gene
• Blended
• Some characteristics, only phenotype matters
  others, genotype as well
• Sex-linked characteristics are on the X
  chromosome
• Genes and environment combine to determine
  expression of some genes
• Scarr-McCartney model of bidirectional influence

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Nature Vs. Nurture

• Genes predict a possible range of outcomes, they
  do not dictate and exact outcome
• Reaction Range
• Canalization
• Gene environment correlation (e.g., niche
  picking)
• Twin studies comparing MZ with DZ twins
• Even MZ twins discordant for some behaviors
• Genes help us choose environment
• Adoption Studies
• Compare whether child more like biological or
  adoptive family
• Historically, self selection of who adopts

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Common Inherited Disease of Childhood

• Inherited Conditions
• Down Syndrome
• PKU
• Cystic Fibrosis
• Tay Sachs Disease

• Conditions presumed at least partly inherited
• Depression
• Diabetes
• Schizophrenia
• Obesity

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• Behavioral Genetics studies contributions of both
  heredity environment to diversity of human
  characteristics
• Environmental Effects
• The special case of maternal stress during
  pregnancy (or maternal genetic high anxiety)
• Hormonal changes change fetal environment
• Stress management or social support intervention
  with pregnant women improved birth weight of
  babies (22 control, 9 treatment group had low
  birth weight babies)

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Prenatal Development

• Conception
• Multiple births maternal age, ethnic background,
  family history, environmental temperature, all
  increase likelihood
• Germinal period (1-2 weeks)
• Embryonic Stage (2-8 weeks)
• Fetal Stage (3rd month until birth)

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Sex Differentiation

• Sperm may be X or Y
• All fetus initially develop gonad tissue
  (undifferentiated)
• At about 7 weeks, if Y, testes develop and begin
  to secrete testosterone which inhibits
  development of female sex organs
• 3 different genes identified
• One switches on hormones
• Two others drive organ development

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Brain Development

• Around 5th month, sucking, blinking observed
• About 6-7 months, fetus can feel pain
  (physiological changes, unclear if there is any
  perception)
• 8th month, recognize different voices and after
  birth, respond to familiar vs. unfamiliar
  differently

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Protecting the developing human

• Placenta
• Vulnerable periods
• Teratogens (agents that damage fetus)
• Tobacco
• Alcohol
• Medications
• Chemicals
• Radiation

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High Risk Pregnancy

• Teen Pregnancy
• Older women
• Medical conditions
• Preterm delivery
• Questions associated with prenatal diagnosis of
  specific conditions

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