Genetics and Prenatal Development

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Chapter 2

• Genetics and Prenatal Development

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Heredity life from a single cell

• Gametes, one from each parent form a zygote
• Zygote formed by meiosis, all other cells
  replicate genetic code by mitosis
• Genes, the basic unit of genetic information, are
  composed of DNA
• Chromosomes, rod-shaped portions of DNA
• 23 pairs (one in each pair from each parent)
• 23rd chromosome determines sex of child

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Multiple Births

• Monozygotic twins
• Single zygote, cluster splits off w/in 1st 2
  weeks
• Identical genetic code
• Dizygotic twins
• 2 separate ovum fertilized 2 zygotes
• Genetic similarities of siblings
• Fertility drugs have increased the chances of
  multiple births (dizyotic)
• Ethnic Differences in likelihood of twins

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Basic Genetics

• Dominant Trait
• Recessive trait
• Genotype
• genetic material present but not observable
• Phenotype
• observable traits
• Homozygous/heterozygous
• Polygenetic traits
• X-linked traits hemophilia, r/g color blindness

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Behavioral Genetics

• Study effects of heredity on behavior
  development
• Genetic disorders
• Down syndrome extra 21st chromosome
• Sickle cell anemia
• Tay-Sachs disease
• Kleinfelters syndrome extra X

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Genetic Counseling

• Karyotype, prior to pregnancy
• Amniocentesis
• CVS - Chorionic Villus Sampling
• Ultrasound sonography

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Infertility

• Possible causes
• Age, previous drug use, low sperm count
• Alternate approaches to conception
• Artificial insemination
• In vitro fertilization
• Surrogate mother

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Multifactorial Transmission

• Human and nonhuman studies find interaction
  between genetics and environment
• Personality traits
• Temperament
• Neuroticism
• Extroversion
• Psychological disorders
• Schizophrenia
• Depression
• Alcoholism
• Autism
• Attention-deficit hyperactive disorder

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Genetic/Environmental Influence S. Scarr

• Active Genotype-environment effects
• Child focus on env. aspect congruent with
  genetically determined abilities
• Passive Genotype-environment effects
• Parents genes produce env. that influences child
• Evocative Genotype-environment effects
• Childs genes elicit a particular type env.

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Prenatal Growth

• Germinal Stage wk 1-2
• Placenta created and attached
• Embryonic stage wk 2-8
• Ectoderm, endoderm, mesoderm
• Major organs begin to be differentiated
• Fetal stage wk 9-40
• Organs become operational

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Teratogens

• Any environmental agent that produces birth
  defect (virus, chemical, or other factor)
• Critical periods for effects
• e.g., Rubella
• Thalidomide
• DES (diethylstibestrol)
• Fetal Alcohol Syndrome

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